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Article

An Anti-Condensation Radiant Heating Floor System in Buildings under Moistening Weather

by
Rong Hu
1,
Jincan Liang
1,
Ting Lan
1,
Yingde Yin
1 and
Gang Liu
2,*
1
School of Architecture and Traffic Engineering, Guilin University of Electronic Technology, Guilin 541004, China
2
School of Energy Science and Engineering, Central South University, Changsha 410083, China
*
Author to whom correspondence should be addressed.
Sustainability 2023, 15(15), 11580; https://doi.org/10.3390/su151511580
Submission received: 10 May 2023 / Revised: 13 July 2023 / Accepted: 22 July 2023 / Published: 26 July 2023
(This article belongs to the Special Issue Enhancement of Heat Transfer and Energy Recovery)
Browse Figures
Review Reports Versions Notes

Abstract

:
In most regions of southern China, condensation frequently occurs on building surfaces during the period from March to April. This phenomenon has been affecting people’s safety and structural properties. This article proposes an innovative anti-condensation floor system based on the reverse Carnot cycle. The evaporation side treats the air and reduces the moisture content, and the heat extracted from the condensation side is recovered by a heat exchanger and transferred to the floor through capillary mats. Simulation studies of the dynamic operation performance have been conducted through the TRNSYS 18 software. The results show that an innovative anti-condensation floor system can effectively keep the floor dry in Guilin. At the same time, regarding the indoor comfort level index, the PMV value is within ±0.5, and the energy consumption of the system is 42% less than that of the cooling dehumidification system. The system also performs well in representative cities where the air moisture content is less than 12 g/kg. This article also provides a reference for the feasibility of radiant floor systems in humid climate areas.

1. Introduction

“Moistening Weather” is a meteorological phenomenon that occurs in portions of South China, primarily between February and April, when the air temperature and humidity rise abruptly after a long period of frigid weather and the air pressure declines drastically [1]. In this weather, air moisture is close to saturation, that is, the relative humidity is close to 100%, but the surface temperature of building envelopes, such as the floor and wall, is lower than the air dew-point temperature, causing condensation and wetting of these surfaces. “Moistening Weather” is not a catastrophic weather event, but it has a negative impact on air quality and human health, causing numerous difficulties in people’s daily lives and work. A moist floor is prone to causing incidents such as slipping and falling, and a humid environment could promote the growth of microbes, which is detrimental to human health [2,3].
In recent years, “Moistening Weather” has garnered a growing amount of social attention. Numerous studies have been conducted to prevent condensation. In engineering, moisture-proof measures such as floor insulation and floor overhangs are typically used to passively elevate the surface temperature. Qian et al. [4] stated that construction with a 50 mm insulation layer (thermal resistance is 0.49 m2·K/W) can help to reduce the condensation risk in Chongqing. Tang et al. [5] optimized a common ventilation overhead floor and proposed a seasonal ventilation control strategy. The average floor temperature was reduced to 0.5 °C in the summer, and the average indoor temperature increased by 1 °C in the winter. Nan et al. [6] proposed overhead floor construction containing an internal closed-air layer. The floor can increase the inner surface temperature by 2 °C compared to ordinary cement floors and contribute to improved heat conservation and moisture resistance. In terms of the building structure, Song et al. [7] pointed out that light wood structure buildings could play a better role in moisture-proof and waterproof performance.
Additionally, an increasing number of dehumidification technologies have been developed. Liquid desiccant is an advanced measure to control air humidity with significant energy-saving potential [8]. Englart et al. [9] proposed a novel liquid desiccant air system that employed a cross-flow hollow-fiber membrane module. The novel system had a higher moisture removal rate in comparison to the conventional system, with an improvement of 28–134%. Zhao et al. [10] developed a novel direct-expansion terminal by combining a flat heat pipe and an air-source heat pump. The indoor humidity ratio experienced a change of between 2.8 and 7.9 g/kg after dehumidification, and the indoor relative humidity could be reduced to a comfortable range within 30 min. Fang et al. [11] firstly presented a cascade deep air dehumidification system integrating a direct-contact cooling module (DCCD) and multi-stage internally cooled liquid desiccant module (MILDD). The results showed that the DCCD–MILDD cascade system can achieve deep air dehumidification with the outlet air humidity ratio lower than 6.2 g/kg and the air-to-solution flow ratios over 4.0 at high-humidity conditions. Salins et al. [12] fabricated a multistage dehumidifier test rig with Calcium Chloride as the desiccant in the present work. The system gave a maximum COP, moisture removal rate, and dehumidification efficiency equal to 2.17, 4.87 g/s, and 73.54%, respectively. Cui et al. [13] proposed carbon dioxide heat pump-driven liquid desiccant dehumidification. The results suggested that the power consumption and dehumidification performance of the desiccant dehumidification systems were reduced and improved by a maximum of 51.67% and 106.89%, respectively, compared with condensing dehumidification. Zhang et al. [14] used condensing dehumidification and liquid desiccant dehumidification methods to achieve the ideal dehumidification process. For liquid desiccant dehumidification, the relative humidity of the air is the most significant factor affecting the COP, whereas for condensing dehumidification, the temperature of the heat sink is the most important factor. Tian et al. [15] proposed the boundary of single-stage and two-stage dehumidification under different conditions, and the energy performance increased as the humidity set point reduced. Ge et al. [16] evaluated the performances of a condensing dehumidifier and the desiccant wheel dehumidifier by exergy analysis. The condensation dehumidifier’s performance was primarily determined by the relative humidity of the indoor air, and its exergy efficiency was 3–4 times that of the desiccant wheel dehumidifier. Li et al. [17] established a circulatory system using liquid desiccant as the medium and realized the ideal reversible dehumidification process. Han et al. [18] introduced a new isothermal dehumidification method for an indoor air conditioning system, in which the cooling mode and isothermal dehumidification mode can be switched by a switching valve. Ge et al. [19] proposed a new air-source heat pump system, which combined radiant cooling/heating for residential buildings. The desiccant wheel and cooling coil completed the dehumidification process together, and the heat required by the desiccant wheel was from the condenser. The composition system can reduce the primary energy requirement by more than 50%. Su et al. [20] adopted a frost-free air conditioning system containing liquid desiccant dehumidification, and the COP and the exergy efficiency increased by 13.02% and 12.73%, respectively. This is an effective strategy for dehumidification in humid regions during the winter. Zhi et al. [21] evaluated the performances of a variable frequency fan to replace the two fans of a traditional solid desiccant dehumidifier. The experimental results of the prototype device showed the dehumidification efficiency was more than 85%. The energy efficiency ratio was improved by 8.1%.
Xu et al. [22] proposed a new air conditioning system with a double-evaporation temperature. Compared with a single-evaporation temperature system, the cooling COP of the double-evaporation temperature system can be increased by 3∼4.2%; the dehumidification capacity was 0.06∼0.61 kg/h, about 1.69∼5.83% higher. Xu et al. [23] proposed an innovative system that combined liquid dehumidification with absorption refrigeration driven by solar energy. The exergy efficiency of the proposed system can reach 16.64%. The maximum moisture removal rate and humidity efficiency in the proposed system were 27.98 g/kg and 0.83 in the rainy season. He et al. [24] proposed a novel structure of a fixed bed, desiccant dehumidification box, constructed and experimented in a sub-tropical city, Guangzhou. The maximum dehumidification capacity could reach 3.9 g/kg and 1.6 g/kg on average. Li et al. [25] proposed a heat pump-driven liquid desiccant dehumidification system. Compared with conventional air-source heat pump dehumidification air conditioning system, the rising ratio of energy efficiency was between 11.4% and 80.7%.
Other methods and measures for preventing dampness in buildings are shown in Table 1. Most previous moisture-proofing measures in public buildings relied primarily on ventilation technologies. Natural ventilation cannot well control the indoor humidity level. In humid and hot climates, natural ventilation would lead to the growth of mold and endanger health and other problems [26]. Mechanical ventilation causes indoor noise and high wind speed generally, which makes people uncomfortable [27,28] and increases energy consumption. The liquid desiccant dehumidifier has a complex structure, and liquid desiccant has corrosion characteristics [29,30]. The desiccant wheel dehumidifier is difficult to integrate with the current air conditioning system and then requires additional power [26].
The methods of solid dehumidification, liquid desiccant dehumidification, and desiccant wheel dehumidification are suitable for industrial buildings with relatively extensive spaces. It is challenging to apply a solution to the problem of floor condensation in ordinary public buildings during moistening weather. Thus, this article proposes an innovative anti-condensation floor system (IAFS), which is based on the principle of the reverse Carnot cycle and the thermal characteristics of a radiant floor. In addition, it also provides a reference for future research on radiation systems.

2. Methodology

2.1. IAFS Principle

As Figure 1 illustrates, the IAFS consists of an evaporator, an air-cooled condenser, a compressor, an expansion valve, a four-way valve, a heat exchanger, capillary mats, and floor construction. The evaporator has an average temperature of 7 °C and can directly chill and dehumidify indoor air. The average condenser temperature is 45 °C, and a portion of the heat extracted from the condenser can be supplied to capillary mats that elevate the interior floor temperature. Figure 1b shows the energy flow diagram of the IAFS, which collects waste heat from part of the condenser and uses it as a heat source for capillary tubes to prevent floor condensation in the room.
To prevent condensation on the floor surface, the temperature of the floor surface must be kept above the dew-point temperature of the air, or the dew-point temperature of the indoor air must be kept below the floor surface temperature. Thus, if only the cooling dehumidification system (CDS) is in operation, the air should be treated and achieve the state of L 1 (Figure 1c). In the IAFS, an interior dehumidifier functions together with the heating floor. As the floor’s surface temperature rises, the moist air only needs to be treated and reaches the state of L 2 . Compared to the process in the CDS, both the dry-bulb temperature and the dew-point temperature of indoor air are increased in the condition with the IAFS. Consequently, the IAFS dehumidification quantity and energy consumption would decrease.
There are generally three radiant systems, and the surface radiant system with capillary mats can produce a quite uniform temperature distribution [37]. In order to ensure the floor surface temperature can be effectively controlled, capillary mats will be applied in the IAFS. A 30 mm XPS insulation layer is laid under the capillary mats, to prevent heat flux through the floor [38]. In addition, the layers above the capillary mats contain a certain thermal mass, so the floor surface temperature will drop slowly even if the active system is turned off, thereby effectively preventing condensation.

2.2. Methods

In order to study the feasibility of the innovative anti-condensation floor system, energy simulation software is used to compare the condensation hours, indoor thermal environment, and system energy consumption in moistening weather for five different floor structures or systems (Table 2).
Moistening weather frequently occurs in southern China, in which doors and windows are often open in public buildings, so the flow rate of natural ventilation is quite high, and the indoor environment is significantly impacted by the outdoor environment. Considering that diverse energy simulation software has distinct computational advantages, DeST and TRNSYS will be used together for computation in this study.
DeST is proficient in ventilation calculation, particularly natural ventilation calculation, whereas TRNSYS excels in HVAC system simulation and energy consumption analysis [39,40]. In transitional seasons, the accuracy of natural ventilation calculation impacts the ultimate results. VentPlus, a module of DeST that has been validated [41,42], can estimate the effect of ventilation on the indoor thermal environment. TRNSYS consists of TRNSYS3D, TRNBuild, TRNEdit, and other modules [43] that focus on system energy simulation and performance analysis. In addition, the TRNSYS software has been utilized successfully in numerous radiation systems analysis studies [44,45,46].
This article utilizes DeST to simulate natural ventilation in a room with the original floor construction (OFC), in which no capillary mat is applied. The results of DeST’s simulations can be utilized to modify the model in TRNSYS. This is the basic model and the reference for system improvement and comparative analysis. The innovative anti-condensation floor system is established, as depicted in Figure 2. In the IAFS, the chiller provides 7 °C chilled water to the coil for dehumidifying the indoor air. A portion of the heat extracted from the condenser can be recovered by an exchanger and stored in a heat storage tank, from which low-temperature hot water of 20 (±1) °C is supplied to the capillary mats embedded in the floor. The refrigerant flow to the heat exchanger is limited to within 70% by a valve to ensure smooth operation, and the remainder is cooled by the ambient air through the air condenser.
The research program is shown in Figure 3. The use of DeST simulates the natural ventilation of the building, and the results are used as input of the indoor air velocity in TRNSYS to calculate the PMV. The difference simulation results of the indoor thermal conditions of the OFC model show that the two software are within 10%.

2.3. Case Study

2.3.1. Climatic Conditions and Building Description

The Hu Huanyong Line divides China into two sections, the northwest and the southeast, with arid weather in the northwest and wet weather in the southeast [47]. Throughout the year, the climate in southern China is relatively humid. Figure 4 displays climate data for the representative cities of Guangzhou, Guilin, Haikou, Xiamen, Changsha, and Wuhan [48]. As the city’s latitude decreases, the mean monthly air temperature and air humidity increase. During the transitional season, particularly in March and April, frigid air from the north collides with warm and humid airflow from the south, causing temperature fluctuations and condensation on the surfaces of building envelopes (Figure 5). In China, this phenomenon is known as “Moistening Weather” [1].
Guilin’s atmospheric temperature and air moisture contents are relatively average compared to the other cities. In this study, a university office building in Guilin serves as an illustration. The indoor thermal environment of the entrance hall is simulated (Figure 5). The hall has a surface area of 249.48 m2 with a depth of 17.6 m, 4.8 m high, and the walls of the front and rear entrances contain a 10 mm thick tempered glass curtain, the door opening area is 5.1 m2, and there are polished floor tiles. The office facility is open from 7 a.m. to 10 p.m., during which time a significant number of people enter and depart through the hall. In Guilin, the average relative humidity for March and April is 78% and 77%, respectively. Under the influence of mild and humid air, the phenomenon of “Moistening Weather” occurs frequently, and the damp and slick polished floor tiles have a significant impact on walking. Based on the climate level of the region, the equipment in the IAFS can be determined and the technical data are shown in Table 3.
IAFS and CDS operation control can be divided into three levels. The first level is the system availability schedule. According to the working schedule of the office building, those systems are available daily from 7:00 to 22:00.
The second is the warning logic of floor condensation. In order to prevent condensation on the floor, the floor temperature must be higher than the indoor air dew-point temperature, and a safety margin must be regarded; hence, the logic relationship can be expressed by Equation (1).
T s ≥ T l + Δ t
For a conventional cooling dehumidifier (CDS), the moisture-proof systems will start if the air dew-point temperature ( T l ) is detected to be higher than the floor temperature minus the temperature margin ( Δ t ). In consideration of Guilin’s humid climate during the transition season, the air dew-point temperature should be controlled below the value ( T s − Δ t ). The safety temperature margin can be set to 1.5 °C due to the rapid change in the air dew-point temperature if the system stops running.
However, because the capillary floor structure has a certain thermal mass in the IAFS, the surface floor temperature is controlled and remains stable, so the safety margin in Equation (1) can be ignored.
The third level refers to the control of the equipment itself.
The performance correction curve for the selected chiller is shown in Figure 6. The outlet water temperature of the chiller and the ambient air temperature influence the cooling capacity and power of the chiller. In TRNSYS (Figure 2), the operating curve of the chiller is a normalized polynomial with ambient and outlet water temperatures as variables.
The module used in TRNSYS is type 206. In order to facilitate data fitting and later change the nominal operating conditions of the unit, the outdoor ambient temperature T a m b and evaporator outlet temperature T e are normalized, as shown in Equations (2) and (3).
T r , a m b = T a m b T o , a m b
T r , e = T e T o , e
After normalization, the calculation equations for the cooling capacity correction coefficient CAP and energy consumption correction coefficient COP are as follows,
C A P r = c 1 + c 2 · T r , a m b + c 3 · T r , a m b 2 + c 4 · T r , e + c 5 · T r , e 2 + c 6 · T r , a m b · T r , e
C O P r = d 1 + d 2 · T r , a m b + d 3 · T r , a m b 2 + d 4 · T r , e + d 5 · T r , e 2 + d 6 · T r , a m b · T r , e
where c and d are constants, which can be obtained by polynomial fitting the manufacturer’s correction curve using MATLAB. The above two performance curve equations are essential data for the successful operation of type 206. The data of Figure 6 are first normalized, and then a polynomial is fitted to the normalized data to obtain the new chiller operating curve, as shown in Figure 7.
In Figure 7, the red stars are the pick points of Figure 6, and the thin blue line is the fitting curve used for the simulation. The X-axis represents the normalized ambient temperature value, the Y-axis represents the normalized outlet water temperature value, and the Z-axis represents the normalized CAP (COP) value.
In this article, TRNSYS was only used for inter-system simulations and did not include the refrigeration cycle. The chilled water is set at 7 °C, and the evaporator temperature is approximately 4 °C.
The flow rate of the chilled water pump can be controlled by adjusting the pump speed. In order to conserve pump power, the water flow rate is reduced to 60% of the nominal flow rate when the floor temperature is 2 °C above the air dew-point temperature, and the frequency is set to 30 Hz (Equation (6)). The flow of the circulating pump depends on the minimum allowed flow of the capillary mats, and it keeps constant.
w h e n   T = T s − T l ≥ 2 , G a = G o × 0.6
Moreover, the fans in the CDS and IAFS operate under their rated operating conditions.

2.3.2. Analysis of Results

The application of the IAFS influences not only the indoor thermal environment level but also the thermal property of the floor; therefore, the characteristics of the IAFS can be analyzed by comparing the performance of various systems, such as IFC vs. OFC, CDS-IFC vs. IFC, and IAFS vs. CDS-OFC.

3. Results

The capillary layer exhibits a heat storage effect that can modify the floor’s performance. In this study, a comparison between the IFC and OFC is conducted to investigate the impact of the capillary structure on floor condensation. Furthermore, the CDS-IFC and IFC comparison results are used for analyzing how a dehumidifier performs on a capillary floor. Lastly, the comparison between the IAFS and CDS-OFC aims to highlight the differences between the new system and conventional dehumidification methods, including the indoor PMV and energy consumption analysis.

3.1. Condensation Risk Control

3.1.1. IFC vs. OFC

As illustrated in Figure 8. a, the condensation on the floor surface is reduced but still exists. The total condensation time of the OFC and IFC during the transitional season (March and April) is 390 h and 309 h, respectively. The IFC has a condensation time that is 81 h shorter than the OFC, particularly in April, when the condensation time decreases by 21%.
In March, when the average ambient temperature is 14.4 °C, the moisture-proof advantage of the IFC is not obvious. In April, the average ambient temperature reaches 19.8 °C. Due to the reason that the layer of capillary mats can increase the thermal mass of the floor as a whole, the surface temperature of the IFC is higher, and the condensation time of the IFC is shorter obviously, compared to the performance of the OFC. However, the surface temperatures of both these floors still fluctuates around the air dew-point temperature. On 2 April, for example, the floor surface temperature of the OFC and IFC is lower than the air dew-point temperature, and condensation appears on the floor all day (Figure 9a).
In the capillary layer of the IFC, due to the water contained in the pipe and the XPS-insulated layer under the capillary, the heat storage characteristics of the floor are enhanced, and the thermal response time of the IFC is prolonged. The heat gained from the outside on the surface of the floor cannot be transferred downwards from the floor in time so that the surface temperature of the floor is increased and more stable than that of the original floor. The floor surface temperature of the IFC is above the dew-point temperature for less time than that of the OFC. In other words, the total condensation time of the IFC is less, but the condensation time of the IFC is still very long without human intervention.

3.1.2. CDS-IFC vs. IFC

In order to prevent condensation on the floor, the conventional cooling dehumidification system (CDS) is first applied, and the results indicate that the composition of the CDS and IFC can effectively prevent condensation. The CDS-IFC reduces the total condensation time to 11.53 h, which is 96% less than the IFC. In March and April, the condensation time of the CDS-IFC is 93% and 99% less than that of the IFC, respectively.
Due to the application of the cooling dehumidification system, the floor surface temperature and air dew-point temperature are lower in the case of the CDS-IFC than in the case of the IFC alone (Figure 8c,d). As the air moisture is removed in the dehumidification process, condensation reduces on the floor. Using the performance on April 2nd as an illustration, the floor surface temperature and air dew-point temperature in the CDS-IFC are lower than in the condition with the IFC alone, but the average floor temperature is 2.67 °C higher than the air dew-point temperature. Even so, the air dew-point temperature is slightly higher than the floor surface temperature at 5 a.m., when the system is not available. For the IFC, the average floor temperature is lower by 0.27 °C than the air dew-point temperature. Hence, the condensation risk exists throughout the day.
After human intervention, a dehumidifier is added to the IFC for dehumidification, the moisture content of indoor air is reduced, and the condensation time is greatly reduced. However, due to the heat storage effect of the IFC, the cold amount at night is stored in the floor, and the floor temperature will be lower than the dew-point temperature before the dehumidifier works in the morning, which will lead to the condensation phenomenon, and when the dehumidifier starts to operate, the condensation phenomenon will disappear.

3.1.3. IAFS vs. CDS-OFC

Compared to the performance of a combination of the CDS and IFC, the condensation time appears to be shorter for the CDS-OFC. This is because the application of the CDS reduces the indoor temperature during the occupied period, whereas the layer of capillary mats in the CDS-IFC could maintain the lower floor temperature at night and until early morning, thereby increasing the risk of condensation (Figure 8a).
The IAFS had the best performance in condensation-proofing. The condensation time during the transitional season is only 15 min (Figure 8a).
Both the CDS-OFC and IAFS are active dehumidification systems. Due to the heating floor in the IAFS, the floor surface temperature is 2.98 °C and 3.12 °C higher than that of the CDS-OFC in March and April, respectively, as well as the air dew-point temperature in the IAFS being slightly higher (Figure 8c,d).
According to the performance on April 2nd (Figure 8b), the indoor air temperature and floor temperature in the IAFS remain relatively stable at night, and the floor surface temperature is higher than that in the CDS-OFC. That is due to the fact that the IAFS contains a certain thermal mass in the floor construction. Although the floor surface temperature in the CDS-OFC increases at night, condensation would occur at 4 am when the floor temperature is below the air dew-point temperature.
The system proposed in this article, the IAFS, collects the waste heat of the condenser and supplies low-temperature hot water to the capillary tube, which makes the floor temperature of the IAFS higher than other systems. In addition, the surface temperature is always higher than the dew-point temperature, and the chance of condensation problems is greatly reduced. Due to the existence of the insulation layer, whether at night or during the day, the floor surface temperature is stable. In the traditional dehumidifier method, air passes through the surface of a coil which is filled with chilled water of 7 °C. As a result, the air moisture reduces, but the indoor temperature and floor temperature will also drop. When the dehumidifier stops working, the nighttime humidity rises once again, raising the dew-point temperature above the floor temperature and causing condensation.

3.2. Indoor Comfort

The performance on April 2nd is taken as an example to show the indoor comfort level in different situations, and the PMV index is used for evaluation. The ambient temperature fluctuates between 17 °C and 22 °C, and the humidity is approximately 13 g/kg on that day.
The weather is moderate in Guilin during the transitional season, and the PMV index approaches zero in the conditions with the OFC and IFC, indicating that the thermal environment is accepted by 95% of occupants (Figure 10).
Cooling devices are used for dehumidification in the CDS-OFC and CDS-IFC, where the indoor air temperatures range from 13.1 °C to 15.5 °C and the mean radiant temperatures vary between 13.6 °C and 15.3 °C. The values of the PMV fall to −0.44 during the occupied period when the dehumidifiers have been put into operation.
In the IAFS, the floor structure contains a certain thermal mass and has a thermal insulation layer. The indoor mean radiation temperature appears stable. During the occupied period, the system provides water of 20 °C to the capillary mats in the floor and supplies cooling to remove the moisture from the indoor air simultaneously, so the indoor environment is acceptable and the PMV is approximately 0 during this time.
The PMV is set to the same clothing factor (0.8 clo) and metabolic rate (2 met) in TRNSYS, and the wind speed is set to the ventilation data referenced from DeST. Based on these data, the impact of air temperature on the PMV is the most important factor. In systems with a dehumidifier, the PMV is low because the dehumidifier directly reduces the air temperature. The PMV of the IFAS is higher than that of a single-run dehumidifier because the floor is supplied with low-temperature hot water. Due to the coupling effect of the indoor dehumidifier and the floor heating, the air temperature under the control of the IFAS is closer to that of systems without operating equipment, and the PMV is similar as well.

3.3. Energy Consumption

As Figure 11 illustrates, the IAFS consumes the least energy among the active systems for dehumidification during the transient season, i.e., 210.54 kWh, while the CDS-OFC and CDS-IFC consume 361.16 kWh and 350.81 kWh, respectively.
The energy conservation of the IAFS occurs mainly in April, and the energy consumption of the IAFS is less than that of the CDS-OFC and CDS-IFC by 49% and 46%, respectively.
In the situations with the CDS, the systems start if the air dew-point temperature is detectable to below the floor temperature minus the temperature margin (1.5 °C), and they work until the end of the occupied period. The indoor air dew-point temperature would increase immediately if the cooling dehumidifiers stop. The CDS-OFC and CDS-IFC work for a long time in March to prevent condensation on the floor (Figure 12a), and dehumidification tasks in April are much heavier for these systems (Figure 12b), because the average outdoor air moisture content has increased in April, and the energy consumption contributed by chillers has increased significantly, accounting for 63% and 60% of the total, respectively.
In the IAFS, the floor temperature is controlled to be higher than the indoor air dew-point temperature. Because the thermal mass above the layer of capillary mats helps to maintain the floor temperature for a period of time, the floor temperature fluctuates little and remains higher than the indoor air dew-point temperature even if the chiller is turned off. Compared to the CDS-OFC and CDS-IFC, the IAFS has a shorter working time and lower dehumidification quantity in March or April (Figure 12). As a result of this, the energy consumption of the IAFS reduces by 42% and 40%, respectively, during the transient season.
In addition, because the ambient temperature in March is lower than in April, the COP of the chiller appears to be greater, i.e., 6.14 in March and 4.92 in April for the CDS-OFC, 6.15 in March and 4.89 in April for the CDS-IFC, and 5.00 in March and 4.79 in April for the IAFS. This is another reason why the chiller’s energy consumption increases in April.
The chiller pumps operate based on Equation (6), and the water flow rate can be changed by adjusting the frequency. Because the floor temperature of the CDS-IFC is close to the air dew-point temperature most of the time (Figure 8c,d), the pump consumes more energy than that of the CDS-OFC in March and April (Figure 11). The fans operate at a constant speed, so the energy consumption is proportional to the duration of operation.
According to the analysis above, the IAFS can effectively prevent floor condensation in the Guilin public building. Compared with the CDS-OFC, the condensation time reduces by 95.6%. The PMV value remains within ±0.5, indicating that the indoor thermal environment is able to maintain a level that is quite comfortable. Moreover, the IAFS consumes 42% less energy than the CDS-OFC.

3.4. Application of IAFS in Other Cities

The research above is based on the weather in Guilin. An extensive study should be carried out for other cities in South China by analyzing the operation performance of the CDS-OFC and IAFS. Cities such as Wuhan, Changsha, Xiamen, Guangzhou, and Haikou are representative.

3.4.1. Condensation Risk Control

The IAFS has positive effects on moisture-proofing in different cities; the condensation time decreases by 55~94% compared with the CDS-OFC. In Wuhan, the IAFS and CDS-OFC have identically effective moisture-proofing properties, meaning that no condensation occurs. Additionally, the higher the latitude of the city, the shorter the condensation time. There are two explanations for this. First, as the city’s latitude falls, the moisture content increases, and the task of dehumidification becomes heavier (Figure 13). Second, the floor temperature decreases at night in the cities located at high latitudes, and it cannot rise at once when the IAFS is put into use, which could lead to condensation in the early morning.

3.4.2. Energy Consumption

Compared with the CDS-OFC, the energy consumption of the IAFS in Wuhan, Changsha, and Xiamen reduces by 69%, 60%, and 22%, respectively. However, the energy consumption of the IAFS is more than that of the CDS-OFC in Guangzhou and Haikou by 15% and 12%, respectively.
The energy consumed by the IAFS performs better than that of the CDS-OFC in the high-latitude cities. The running duration of the CDS-OFC is much larger than that of the IAFS to prevent floor condensation, and then the corresponding energy consumption is higher than that of the IAFS in the high-latitude cities, like Wuhan. Conversely, the energy consumption of the IAFS increases in Haikou (at low latitude), where dehumidification increases, and the cooling requirement increases as the room temperature grows. In addition, the relatively higher ambient temperature could make the chiller COP decrease in the city. Hence, energy consumption increases.
In South China, the moisture content gradually increases with the decrease in latitude and being closer to the sea, and the condensation risk in this region increases (Figure 4b and Figure 13a). It is discovered that both the CDS and IAFS can prevent condensation effectively, but the IAFS performs better in most southern cities, such as Wuhan, Changsha, Guilin, etc. The weather is quite cold in the winter, and the average room temperature stays at around 14.5 °C during the transient season, while the air moisture content increases as the outdoor air temperature goes up quickly. Therefore, the IAFS can effectively maintain a comfortable environment with less energy consumption. However, in a city with high moisture content and warm weather, like Haikou, the IAFS can still keep the floor dry but at a slightly higher energy cost. According to Figure 13, the IAFS is suitable for the cities where average air moisture is less than 12 g/kg in South China.

4. Discussion

This article proposes a novel system for condensation prevention, presenting distinct advantages compared with other dehumidification methods. This system is compact and suitable for civil buildings and cost-cheap. The system can be utilized as long as waste heat is available, not solely limited to the waste heat generated by the air-source heat pump mentioned in this article.
Moreover, a comparative simulation was conducted using DeST and TRNSYS. Both of these tools are HVAC modeling tools, but DeST focuses on building thermal physics, including ventilation in particular. While TRNSYS performs a broad variety of functions, its role in HVAC applications tends toward the simulation and analysis of system energy consumption. Both tools utilized in this work have obtained the ASHARE 140 certification [50]. All the employed meteorological data files come from Chinese Standard Weather Data and meteorological station data. The system’s device data are derived from the enterprise’s publicly available performance characteristics. The simulation of the original building produced outcomes that were in accordance with real-life scenarios. This means that performing simulation studies on various systems and obtaining simulation results have specific reference values for the same building.
According to a comparison of the simulation results, the floor with a capillary layer is useful in avoiding condensation. After providing low-temperature hot water to the capillary while the dehumidifier is operating inside, the indoor PMV and energy consumption performance of the IAFS is better than that of the traditional method, CDS-OFC. This method is fresh and offers a guide for resolving moisture problems in southern cities. The place with the similar moisture weather accounts for about 26% of China’s total land area (about 2.5 million square kilometers), but it has 58% of the country’s people (about 823.4 million people). It is important to investigate and resolve moisture problems due to the extent of the potentially impacted area.
This study has some space for improvement. Currently, it is not practical to perform testing in different cities owing to the vast variety of locations involved, and the condensation occurrence time is unclear because it is affected by local weather. Furthermore, this study explored the differences in indoor PMV and system energy consumption under different methods. The fluid dynamics within the room have not been further explored, and the effect of the air outlet location on the inside wind speed field has not been taken into account.
The effect of various moisture contents on condensation humidity in this study may be explored further in the future by experimental testing in a climatic experiment chamber.

5. Conclusions

This study aims to solve the moisture problem in public buildings in the transient season in the region of the middle and lower reaches of the Yangtze River and the places in southern China, where “Moistening Weather” usually appears in March and April. An innovative anti-condensation floor system (IAFS) based on the reverse Carnot cycle was proposed. The TRNSYS software was used to study the feasibility of the IAFS to prevent condensation, as well as the indoor comfort level and energy consumption. The results showed that the IAFS has a positive effect on preventing condensation on the floor. An entrance hall in an office building in Guiling was taken as an example, and the condensation time is as small as 0.32 h. In addition, the indoor PMV is within ±0.5, indicating that the thermal environment is at a high comfort level, and the energy consumption of the IAFS is 42% less than that of the CDS-OFC. In addition, further research revealed that the IAFS has an excellent effect on preventing condensation in other cities in South China. The energy consumption of the system decreases by 69%, 60%, and 22% in Wuhan, Changsha, and Xiamen, respectively, but the energy consumption of the system increases by 15% and 12%, respectively, in Guangzhou and Haikou, due to the high ambient temperature and the COP of the chiller falling. In addition, the indoor temperature increases causing the energy consumption increases is also one of the reasons. According to the study, the IAFS can be applied in most regions in the middle and lower reaches of the Yangtze River and the cities of southern China to prevent condensation on the floor surface. In the future, the experiment test of different moisture content on the floor condensation can be carried out through the climatic experiment chamber, so as to conveniently obtain different urban climate conditions and conduct research on the prevention of condensation.

Author Contributions

All authors contributed to the study conception and design. R.H.: Conceptualization, writing—review and editing. J.L.: Software—simulation, data curation, data analysis, writing—original draft. T.L.: Material preparation, data collection, writing—original draft. Y.Y.: Writing—review and editing, supervision. G.L.: Supervision, investigation. All authors commented on previous versions of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This work is supported by the Guangxi Science and Technology base and talent programme (NO.AD20159012) and the Guangxi Natural Science Foundation (NO. 2018GXNSFBA050022),and the Science Foundation of Guilin University of Electronic Technology (NO. UF19001Y).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Available after request.

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

cHeat pump ambient temperature correction factor
CAPrNormalized cooling capacity
COPrNormalized coefficient of performance
dHeat pump outlet water temperature correction factor
GaWater flow after pump frequency conversion, m3/h
GoRated water flow of pump, m3/h
TaIndoor air temperature, °C
TambAmbient temperature, °C
TeOutlet water temperature, °C
TlIndoor air dew-point temperature, °C
To,ambAmbient temperature of heat pump standard conditions, °C
To,eOutlet water temperature of heat pump standard conditions, °C
Tr,ambNormalized ambient temperature
Tr,eNormalized outlet water temperature
TsFloor surface temperature, °C
TwSupply water temperature, °C
CAPChiller cooling capacity
CDSCooling dehumidification system
COPCoefficient of performance
IAFSInnovative anti-condensation floor system
IFCInnovative floor with capillary mats
OFCOriginal floor construction without capillary mats
PMVPredicted mean vote
XPSExtrusion polystyrene insulation

References

  1. Zhang, Y.; Wu, Z.; Zhang, M.; Mai, J.; Jin, L.; Wang, F. Smart Indoor Humidity and Condensation Control in the Spring in Hot-Humid Areas. Build. Environ. 2018, 135, 42–52. [Google Scholar] [CrossRef]
  2. Du, C.; Li, B.; Zhao, Z.; Norbäck, D.; Cai, J.; Deng, Q.; Lu, C.; Qian, H.; Zheng, X.; Zhang, X.; et al. Home Dampness/Mold(D/M) Improvement in Children’s Residences over the Past Decade in China-a Comparison of Repeated Surveys in 2010 and 2019. Build. Environ. 2021, 205, 108181. [Google Scholar] [CrossRef]
  3. Mendell, M.J.; Macher, J.M.; Kumagai, K. Measured Moisture in Buildings and Adverse Health Effects: A Review. Indoor Air 2018, 28, 488–499. [Google Scholar] [CrossRef]
  4. Qian, H.; Tang, M.; Wang, D.; Fang, J. Effect of Insulation Ground on Anti-Condensation in Rural Residence. Procedia Eng. 2017, 180, 91–98. [Google Scholar] [CrossRef]
  5. Tang, M.; Lin, X.; Xu, Y.; Ren, J.; Qian, H. Study on the Optimization of Ground Damp-proofing in Rural Residence in Hot Summer and Cold Winter Zone. Build Sci. 2022, 38, 113–118. [Google Scholar] [CrossRef]
  6. Nan, Y.; Feng, Y.; Zhong, H.; Liu, Y. Damp Proof Design for Raised Floors of Rammed Earth Folk House in Sichuan and Chongqing. Build Sci. 2015, 31, 90–94. [Google Scholar] [CrossRef]
  7. Song, J.; Yu, X.; Zhang, Z. Moisture-proof Engineering Measures of Light Wood Frame Construction. Architect. Technol. 2011, 42, 596–598. [Google Scholar]
  8. Yue, L.; Yonggao, Y.; Xingwang, Z.; Chengbin, Z. Effects of Liquid-Desiccant Air Conditioning Processes on the Presence of Inhalable Particles in the Air. Build. Environ. 2021, 194, 107662. [Google Scholar] [CrossRef]
  9. Englart, S.; Rajski, K. A Novel Membrane Liquid Desiccant System for Air Humidity Control. Build. Environ. 2022, 225, 109621. [Google Scholar] [CrossRef]
  10. Zhao, H.; Wu, Y.; Lin, B.; Sun, H. Experimental investigation on the improvement of cooling and dehumidification of a direct-expansion terminal integrated with flat heat pipe. Energy Build. 2022, 260, 111922. [Google Scholar] [CrossRef]
  11. Fang, S.; Xu, Z.; Zhou, X.; Zhang, H.; Zhi, X.; Qiu, L. Cascade deep air dehumidification with integrated direct-contact cooling and liquid desiccant absorption. Energy Convers. Manag. 2022, 268, 115959. [Google Scholar] [CrossRef]
  12. Salins, S.S.; Kota Reddy, S.V.; Kumar, S. Effect of Climatic Conditions on the Performance of a Multistage Dynamic Dehumidifier Test Rig. Build. Environ. 2021, 205, 108245. [Google Scholar] [CrossRef]
  13. Cui, Q.; Qu, H.; Sun, B.; Gao, E.; Zhang, X. Operating characteristics and performance evaluation of carbon dioxide heat pump driven liquid desiccant dehumidification systems: A comparative study. Energy Convers. Manag. 2022, 254, 115298. [Google Scholar] [CrossRef]
  14. Zhang, L.; Liu, X.-H.; Jiang, Y. Ideal Efficiency Analysis and Comparison of Condensing and Liquid Desiccant Dehumidification. Energy Build. 2012, 49, 575–583. [Google Scholar] [CrossRef]
  15. Tian, S.; Su, X.; Geng, Y.; Li, H.; Liang, Y.; Di, Y. Heat Pump Combined with Single-Stage or Two-Stage Desiccant Wheel System? A Comparative Study on Different Humidity Requirement Buildings. Energy Convers. Manag. 2022, 255, 115345. [Google Scholar] [CrossRef]
  16. Ge, F.; Wang, C. Exergy Analysis of Dehumidification Systems: A Comparison between the Condensing Dehumidification and the Desiccant Wheel Dehumidification. Energy Convers. Manag. 2020, 224, 113343. [Google Scholar] [CrossRef]
  17. Li, Z.; Liu, X.-H.; Lun, Z.; Jiang, Y. Analysis on the Ideal Energy Efficiency of Dehumidification Process from Buildings. Energy Build. 2010, 42, 2014–2020. [Google Scholar] [CrossRef]
  18. Han, X.; Zhang, X.; Wang, L.; Niu, R. A Novel System of the Isothermal Dehumidification in a Room Air-Conditioner. Energy Build. 2013, 57, 14–19. [Google Scholar] [CrossRef]
  19. Ge, F.; Guo, X.; Hu, Z.; Chu, Y. Energy Savings Potential of a Desiccant Assisted Hybrid Air Source Heat Pump System for Residential Building in Hot Summer and Cold Winter Zone in China. Energy Build. 2011, 43, 3521–3527. [Google Scholar] [CrossRef]
  20. Su, W.; Li, H.; Sun, B.; Li, S.; Zhang, X. Performance Investigation on a Frost-Free Air Source Heat Pump System Employing Liquid Desiccant Dehumidification and Compressor-Assisted Regeneration Based on Exergy and Exergoeconomic Analysis. Energy Convers. Manag. 2019, 183, 167–181. [Google Scholar] [CrossRef]
  21. Zhi, Y.; Yang, X. Household solid desiccant dehumidifier with multiple operating modes: Concept and prototype device. J. Build. Eng. 2023, 66, 105964. [Google Scholar] [CrossRef]
  22. Xu, S.; Niu, J.; Ma, H.; Ma, G. Cooling and Dehumidification Performance Study of a New Air Conditioning System with Double Evaporation Temperature. Energy Build. 2023, 295, 113294. [Google Scholar] [CrossRef]
  23. Xu, A.; Wang, Y.; Song, T.; Xie, N.; Liu, Z. Thermodynamic analyses of an innovative system combined dehumidification, cooling and heating driven by solar energy. Energy Convers. Manag. 2023, 279, 116757. [Google Scholar] [CrossRef]
  24. He, F.; Yang, W.; Ling, Z.Y.; Ling, Z. Comparative investigation on performance of single-stage and double-stage desiccant dehumidification boxes under hot-humid climatic conditions. Int. J. Refrig. 2023, 146, 109–120. [Google Scholar] [CrossRef]
  25. Li, W.; Yin, Y.; Wang, Y. Performance evaluation of a heat pump-driven liquid desiccant dehumidification system integrated with fresh air supply. Energy Build. 2022, 275, 112473. [Google Scholar] [CrossRef]
  26. Shamim, J.A.; Hsu, W.-L.; Paul, S.; Yu, L.; Daiguji, H. A Review of Solid Desiccant Dehumidifiers: Current Status and near-Term Development Goals in the Context of Net Zero Energy Buildings. Renew. Sustain. Energy Rev. 2021, 137, 110456. [Google Scholar] [CrossRef]
  27. de Dear, R.J.; Akimoto, T.; Arens, E.A.; Brager, G.; Candido, C.; Cheong, K.W.D.; Li, B.; Nishihara, N.; Sekhar, S.C.; Tanabe, S.; et al. Progress in Thermal Comfort Research over the Last Twenty Years. Indoor Air 2013, 23, 442–461. [Google Scholar] [CrossRef] [Green Version]
  28. Zhu, Y.; Luo, M.; Ouyang, Q.; Huang, L.; Cao, B. Dynamic Characteristics and Comfort Assessment of Airflows in Indoor Environments: A Review. Build. Environ. 2015, 91, 5–14. [Google Scholar] [CrossRef]
  29. Lowenstein, A. Review of Liquid Desiccant Technology for HVAC Applications. HVAC&R Res. 2008, 14, 819–839. [Google Scholar] [CrossRef]
  30. Rafique, M.M.; Gandhidasan, P.; Bahaidarah, H.M.S. Liquid Desiccant Materials and Dehumidifiers—A Review. Renew. Sustain. Energy Rev. 2016, 56, 179–195. [Google Scholar] [CrossRef]
  31. Wang, L.; Wang, G. Application of temperature and humidity independent control to a combined workshop of a cigarette factory in Shanghai. Heat. Vent. Air Cond. 2015, 8, 73–76. [Google Scholar]
  32. Abdullah, S.; Zubir, M.N.B.M.; Muhamad, M.R.B.; Newaz, K.M.S.; Öztop, H.F.; Alam, M.S. Technological development of evaporative cooling systems and its integration with air dehumidification processes: A review. Energy Build. 2023, 283, 112805. [Google Scholar] [CrossRef]
  33. Qi, R.; Dong, C.; Zhang, L. A review of liquid desiccant air dehumidification: From system to material manipulations. Energy Build. 2020, 215, 109897. [Google Scholar] [CrossRef]
  34. Chen, R.; Li, Y. Property Equipment and Facilities Management, 3rd ed.; Beijing Institute of Technology Press: Beijing, China, 2021; p. 158. [Google Scholar]
  35. Min, Y.; Shi, W.; Shen, B.; Chen, Y.; Yang, H. Enhancing the cooling and dehumidification performance of indirect evaporative cooler by hydrophobic-coated primary air channels. Int. J. Heat Mass Transf. 2021, 179, 121733. [Google Scholar] [CrossRef]
  36. Hu, R.; Lu, L.; Lu, J.; Liang, C.; Lan, T.; He, Z. A Moisture-proof System of Building Envelope Surface Based on Inverse Carnot Cycle. CN216203898U, 5 April 2022. [Google Scholar]
  37. Hu, R.; Niu, J.L. A Review of the Application of Radiant Cooling & Heating Systems in Mainland China. Energy Build. 2012, 52, 11–19. [Google Scholar] [CrossRef]
  38. Li, B. Application and Characteristic of the Heating System with Low-temperature Hot-water Floor Radiation. J. North China Univ. Water Resour. Electr. Power (Nat. Sci. Ed.) 2007, 4, 45–47. [Google Scholar] [CrossRef]
  39. Zheng, M.; Pan, S. Application as Commissioning Tool of Various HVAC Simulation Programs and Visual Tools. In Proceedings of the 10th International Building Performance Simulation Association Conference and Exhibition-Building Simulation, Beijing, China, 3 September 2007; pp. 1975–1982. [Google Scholar]
  40. Crawley, D.B.; Hand, J.W.; Kummert, M.; Griffith, B.T. Contrasting the Capabilities of Building Energy Performance Simulation Programs. Build. Environ. 2008, 43, 661–673. [Google Scholar] [CrossRef] [Green Version]
  41. Yan, D.; Xia, J.; Tang, W.; Song, F.; Zhang, X.; Jiang, Y. DeST—An Integrated Building Simulation Toolkit Part I: Fundamentals. Build. Simul. 2008, 1, 95–110. [Google Scholar] [CrossRef]
  42. Zhang, M. Study on Coupled Natural Ventilation Simulation Analysis and Design Guide. Master’s Thesis, Tsinghua University, Beijing, China, 2011. [Google Scholar]
  43. TRNSYS. Transient System Simulation Tool. Available online: http://www.trnsys.com (accessed on 20 September 2022).
  44. Ma, X.; Wang, X. Simulation on Solar Assisted Air Source Heat Pump Heating System in Rural House by Using TRNSYS. IOP Conf. Ser. Earth Environ. Sci. 2020, 508, 012035. [Google Scholar] [CrossRef]
  45. Lu, S.; Zhao, Y.; Fang, K.; Li, Y.; Sun, P. Establishment and Experimental Verification of TRNSYS Model for PCM Floor Coupled with Solar Water Heating System. Energy Build. 2017, 140, 245–260. [Google Scholar] [CrossRef]
  46. Atienza Márquez, A.; Cejudo López, J.M.; Fernández Hernández, F.; Domínguez Muñoz, F.; Carrillo Andrés, A. A Comparison of Heating Terminal Units: Fan-Coil versus Radiant Floor, and the Combination of Both. Energy Build. 2017, 138, 621–629. [Google Scholar] [CrossRef]
  47. “China Geography Encyclopedia” Series Editorial Committee. Gaoligong Shan; World Publishing Corporation Guangdong Branch: Guangzhou, China, 2017; pp. 16–17. [Google Scholar]
  48. Zhang, Y.; Mai, J.; Zhang, M.; Wang, F.; Zhai, Y. Adaptation-Based Indoor Environment Control in a Hot-Humid Area. Build. Environ. 2017, 117, 238–247. [Google Scholar] [CrossRef]
  49. Air Cooled Chiller/Air Source Heat Pump YCAC Series. Available online: http://file.co188.com/ebook/openEBook2.action?bookId=1145700435775&pageNo=0 (accessed on 20 September 2022).
  50. Jiang, Y.; Shi, X.; Zhou, X.; Jin, X.; An, J.; Yan, D. Comparison and Verification of the Simulation Results of DeST Based on ASHARE-140 Standard. In Proceedings of the 16th IBPSA Conference, Rome, Italy, 2–4 September 2019; pp. 1506–1513. [Google Scholar]
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Figure 1. IAFS principle. (a) The principle of IAFS [36]. (b) Energy flow of IAFS. 1: compressor, 2: valve, 3: condenser, 4: expansion valve, 5: evaporator, 6: coil, 7: fan, 8: pump, 9: heat exchanger, 10: tank, 11: capillary mat layer; the solid lines are water cycle, and the imaginary line is refrigerant cycle. (c) Air handling process in IAFS: the x axis (d) is humidity, the y axis (T) is air temperature, and the blue curve is 100% relative humidity curve; A: indoor air state in CDS, A ′ : indoor air state in IAFS, S 1 : floor surface temperature in CDS, S 2 : floor surface temperature in IAFS, L 1 : air state of the outlet of CDS, L 2 : air state of the outlet of IAFS.
Figure 1. IAFS principle. (a) The principle of IAFS [36]. (b) Energy flow of IAFS. 1: compressor, 2: valve, 3: condenser, 4: expansion valve, 5: evaporator, 6: coil, 7: fan, 8: pump, 9: heat exchanger, 10: tank, 11: capillary mat layer; the solid lines are water cycle, and the imaginary line is refrigerant cycle. (c) Air handling process in IAFS: the x axis (d) is humidity, the y axis (T) is air temperature, and the blue curve is 100% relative humidity curve; A: indoor air state in CDS, A ′ : indoor air state in IAFS, S 1 : floor surface temperature in CDS, S 2 : floor surface temperature in IAFS, L 1 : air state of the outlet of CDS, L 2 : air state of the outlet of IAFS.
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Figure 2. TRNSYS model of IAFS.
Figure 2. TRNSYS model of IAFS.
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Figure 3. Research program.
Figure 3. Research program.
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Figure 4. Urban climate. (a) is the atmospheric temperatures; (b) is the air moisture contents.
Figure 4. Urban climate. (a) is the atmospheric temperatures; (b) is the air moisture contents.
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Figure 5. A public building in Guilin.
Figure 5. A public building in Guilin.
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Figure 6. Manufacturer correction curves [49].
Figure 6. Manufacturer correction curves [49].
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Figure 7. Chiller engine running curve. (a) Cooling capacity correction curve: blue line is fitting correction curve, red star corrects the curve scatter for the manufacturer; (b) COP correction curve: blue line is fitted correction curve, red star corrects the curve scatter for the manufacturer.
Figure 7. Chiller engine running curve. (a) Cooling capacity correction curve: blue line is fitting correction curve, red star corrects the curve scatter for the manufacturer; (b) COP correction curve: blue line is fitted correction curve, red star corrects the curve scatter for the manufacturer.
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Figure 8. Condensation risk results for individual systems. (a) Total condensation time; (b) condensation time at occupied period; (c) average floor surface temperature vs. average air dew-point temperature in March; (d) average floor surface temperature vs. average air dew-point temperature in April.
Figure 8. Condensation risk results for individual systems. (a) Total condensation time; (b) condensation time at occupied period; (c) average floor surface temperature vs. average air dew-point temperature in March; (d) average floor surface temperature vs. average air dew-point temperature in April.
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Figure 9. System simulation hourly results on April 2nd. (a) The hourly temperatures in OFC and IFC; (b) the hourly temperatures in CDS-OFC, CDS-IFC, and IAFS.
Figure 9. System simulation hourly results on April 2nd. (a) The hourly temperatures in OFC and IFC; (b) the hourly temperatures in CDS-OFC, CDS-IFC, and IAFS.
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Figure 10. PMV values of different systems on April 2nd.
Figure 10. PMV values of different systems on April 2nd.
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Figure 11. System energy consumption. (a) is the energy consumption in March; (b) is the energy consumption in April; (c) is the total energy consumption.
Figure 11. System energy consumption. (a) is the energy consumption in March; (b) is the energy consumption in April; (c) is the total energy consumption.
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Figure 12. System equipment. (a) is the running duration of the equipment; (b) is the moisture removed by the device.
Figure 12. System equipment. (a) is the running duration of the equipment; (b) is the moisture removed by the device.
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Figure 13. Regional correlation. (a) The correlation of latitude with average moisture content and total condensation time; (b) the correlation of average moisture content with moisture removed and energy consumption.
Figure 13. Regional correlation. (a) The correlation of latitude with average moisture content and total condensation time; (b) the correlation of average moisture content with moisture removed and energy consumption.
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Table
Table 1. Characteristics of different dehumidification methods and measures.
Table 1. Characteristics of different dehumidification methods and measures.
Methods
/Measures		CostEfficiencyDurability
Solid
Desiccant [31,32]		Low investment and operating costsLess stableLimits practical applications and needs regeneration
Liquid
Desiccant [31,33]		High initial investmentEffectively controls the indoor humidityHigh-temperature heat source and high salt solution consumption
Cooling
Dehumidification [34,35]		High initial investment and operating costsStable and reliableFree from cross-contamination and convenient management
VentilationRelatively lowLowSusceptible to the influence of external environmental factors
Table
Table 2. Systems configurations.
Table 2. Systems configurations.
Floor Structure/SystemDescribe
OFCOriginal floor construction without capillary mats
IFCInnovative floor with capillary mats
CDS-OFCCooling dehumidifier used in the room with OFC
CDS-IFCCooling dehumidifier used in the room with IFC
IAFSInnovative anti-condensation floor system
Table
Table 3. Main system parameters.
Table 3. Main system parameters.
EquipmentTechnical ParameterSystem Involved
ChillerAir-Cooled ChillerCDS-OFC
Cooling capacity: 13.9 kWCDS-IFC
Rated power: 5.1 kWIAFS
Chilled water pumpWater flow rate: 1.6 m3/hCDS-OFC
Water lift: 16 mCDS-IFC
Rated power: 0.37 kWIAFS
Circulation pumpWater flow rate: 1.1 m3/hIAFS
Water lift: 8.5 m
Rated power: 0.18 kW
Capillary matPipe spacing: 20 mmIAFS
Diameter: 4.3 mm pipeIFC
Wall thickness: 0.8 mm
Fan coilSupply air flow rate: 1020 m3/hCDS-OFC
Rated power: 0.16 kWCDS-IFC
IAFS
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Hu, R.; Liang, J.; Lan, T.; Yin, Y.; Liu, G. An Anti-Condensation Radiant Heating Floor System in Buildings under Moistening Weather. Sustainability 2023, 15, 11580. https://doi.org/10.3390/su151511580

AMA Style

Hu R, Liang J, Lan T, Yin Y, Liu G. An Anti-Condensation Radiant Heating Floor System in Buildings under Moistening Weather. Sustainability. 2023; 15(15):11580. https://doi.org/10.3390/su151511580

Chicago/Turabian Style

Hu, Rong, Jincan Liang, Ting Lan, Yingde Yin, and Gang Liu. 2023. "An Anti-Condensation Radiant Heating Floor System in Buildings under Moistening Weather" Sustainability 15, no. 15: 11580. https://doi.org/10.3390/su151511580

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