Evaluation of the Use of Different Dedicated Mechanical Subcooling (DMS) Strategies in a Water Source Transcritical CO2 Heat Pump for Space Heating Applications
Abstract
:1. Introduction
2. Numerical Modelling
- CO2 cycle with DMS and with IHX with the DMS evaporator located upstream the IHX. This configuration is denoted as Conf. C in the standard configuration and it is denoted as Conf. C* when the water flow is reversed.
- CO2 cycle with DMS with the DMS evaporator located downstream the IHX. This configuration is denoted as Conf. D. In the case of Conf. D* the configuration is similar but in this case, the water flow is reversed.
- Water splitting strategy with a CO2 cycle with DMS with the DMS evaporator located downstream the IHX. This configuration was denoted as Conf. E*. Note that in this case the water flow to be heated is divided into two different streams, one sent to the condenser of the DMS cycle and the other to the gas cooler. Conf. E corresponds to the case where no IHX is used.
3. Results and Discussion
4. Conclusions
- As the improvement obtained with a water splitting strategy with DMS and IHX (Figure 3) with respect to the base cycle with IHX (Figure 1) depends on the temperature range considered, it is highly recommended to evaluate the application when selecting the configuration to be used. For the case of space heating applications with temperature ranges of 40/45 °C, this DMS option provides an improvement of 25% in the optimal COP values reached by the system. However, in the case of water pool heating applications in indoor swimming pools (25/30 °C), the improvement is reduced to 5%.
- When the configurations of Figure 3 (Conf. G and F) are not considered, the base CO2 cycle with IHX but without DMS is the best option when the system works under optimal gas cooler pressure conditions.
- When all the coupling strategies between the DMS cycle and the CO2 heat pump are compared, optimal COP values obtained can vary up to 30% whereas the optimal operating pressure of the CO2 cycle can vary up to 8%.
- Regarding key design parameters, an optimal compressor speed of 2100 rpm was found for Conf. G. (i.e., configuration of Figure 3 with IHX). Moreover, the optimal water flow splitting strategy for this configuration was the case of heating 15% of the water flow at the gas cooler and 85% of the water flow at the DMS condenser.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
- Nekså, P.; Rekstad, H.; Zakeri, G.; Schiefloe, P. CO2 heat pump water heater: Characteristics, system, design and experimental results. Int. J. Refrig. 1998, 21, 172–179. [Google Scholar] [CrossRef]
- Velasco, F.; Haddouche, M.; Illán-Gómez, F.; García-Cascales, J. Experimental characterization of the coupling and heating performance of a CO2 water-to-water heat pump and a water storage tank for domestic hot water production system. Energy Build. 2022, 265, 112085. [Google Scholar] [CrossRef]
- Hepbasli, A.; Biyik, E.; Ekren, O.; Gunerhan, H.; Araz, M. A key review of wastewater source hat pump (WWSHP) system. Energy Convers. Manag. 2014, 88, 700–722. [Google Scholar] [CrossRef]
- Culha, O.; Gunerhan, H.; Biyik, E.; Ekren, O.; Hepbasli, A. Heat exchanger applications in wastewater source heat pumps for buildings: A key review. Energy Build. 2015, 104, 215–232. [Google Scholar] [CrossRef]
- Shen, C.; Lei, Z.; Wang, Y.; Zhang, C.; Yao, Y. A review of the current research and application of wastewater source heat pumps in China. Therm. Sci. Eng. Prog. 2018, 6, 140–156. [Google Scholar] [CrossRef]
- Mazhar, A.R.; Liu, S.; Shukla, A. A Key Review of Non-Industrial Greywater Heat Harnessing. Energies 2018, 11, 386. [Google Scholar] [CrossRef] [Green Version]
- Shen, C.; Jiang, Y.; Yao, Y.; Wang, X. An experimental comparison of two heat exchangers used in wastewater source heat pump: A novel dry-expansion shell-and-tube evaporator versus a conventional immersed evaporator. Energy 2012, 47, 600–608. [Google Scholar] [CrossRef]
- Baek, N.; Shin, U.; Yoon, J. A study on the design and analysis of a heat pump heating system using wastewater as a heat source. Sol. Energy 2005, 78, 427–440. [Google Scholar] [CrossRef]
- Gu, Y.; Deng, H. The Feasibility Analysis of Wastewater Source Heat Pump Using the Urban Wastewater Heat. Res. J. Appl. Sci. Eng. Technol. 2012, 4, 3501–3504. [Google Scholar]
- Tassou, S. Heat recovery from sewage effluent using heat pumps. Heat Recover. Syst. CHP 1988, 8, 141–148. [Google Scholar] [CrossRef]
- Ni, L.; Lau, S.; Li, H.; Zhang, T.; Stansbury, J.; Shi, J.; Neal, J. Feasibility study of a localized residential grey water energy-recovery system. Appl. Therm. Eng. 2012, 39, 53–62. [Google Scholar] [CrossRef]
- Zhong, Z.W.; Li, J.X. Sewage Heat Source Pump System’s Application Examples and Prospect Analysis in China. In Proceedings of the International Refrigeration and Air Conditioning Conference, West Lafayette, IN, USA, 12–15 July 2004; Paper 734. Available online: http://docs.lib.purdue.edu/iracc/734 (accessed on 1 June 2022).
- Liu, Z.; Ma, L.; Zhang, J. Application of a heat pump system using untreated urban sewage as a heat source. Appl. Therm. Eng. 2014, 62, 747–757. [Google Scholar] [CrossRef]
- Kahraman, A.; Çelebi, A. Investigation of the Performance of a Heat Pump Using Waste Water as a Heat Source. Energies 2009, 2, 697–713. [Google Scholar] [CrossRef]
- Chao, S.; Yiqiang, J.; Yang, Y.; Shiming, D.; Xinlei, W. A field study of a wastewater source heat pump for domestic hot water heating. Build. Serv. Eng. Res. Technol. 2012, 34, 433–448. [Google Scholar] [CrossRef]
- Coşkun, S.; Motorcu, A.R.; Yamankaradeniz, N.; Pulat, E. Evaluation of control parameters’ effects on system performance with Taguchi method in waste heat recovery application using mechanical heat pump. Int. J. Refrig. 2012, 35, 795–809. [Google Scholar] [CrossRef]
- Shen, C.; Yang, L.; Wang, X.; Jiang, Y.; Yao, Y. An experimental and numerical study of a de-fouling evaporator used in a wastewater source heat pump. Appl. Therm. Eng. 2014, 70, 501–509. [Google Scholar] [CrossRef]
- Hervas-Blasco, E.; Navarro-Peris, E.; Barcelo-Ruescas, F.; Corberán, J.M. Improved water to water heat pump design for low-temperature waste heat recovery based on subcooling control. Int. J. Refrig. 2019, 106, 374–383. [Google Scholar] [CrossRef]
- Nehm, G.; Palandre, L.; Clodic, D.F. High Efficiency Heat Pump for Domestic Hot Water Generation. In Proceedings of the International Refrigeration and Air Conditioning Conference, West Lafayette, IN, USA, 14–17 July 2008; Paper 953. Available online: http://docs.lib.purdue.edu/iracc/95 (accessed on 3 June 2022).
- Wang, H.; Wang, Q.; Chen, G. Experimental performance analysis of an improved multifunctional heat pump system. Energy Build. 2013, 62, 581–589. [Google Scholar] [CrossRef]
- Yamankaradeniz, N.; Coşkun, S.; Muhiddin, C.A.N. Comparison Between Conventional System and Heat Pump for Energy Saving in Textile Industry by Utilizing Waste Heat. J. Uludag Univ. Fac. Eng. Archit. 2007, 12, 115–124. [Google Scholar] [CrossRef]
- Otón-Martínez, R.A.; Illán-Gómez, F.; García-Cascales, J.R.; Velasco, F.; Haddouche, M.R. Impact of an internal heat exchanger on a transcritical CO2 heat pump under optimal pressure conditions. Appl. Therm. Eng. 2022, 215, 118991. [Google Scholar] [CrossRef]
- Illán-Gómez, F.; Sena Cuevas, V.F.; García-Cascales, J.R.; Velasco, F.J.S. Analysis of the optimal gas cooler pressure of a CO2 heat pump with gas bypass for hot water generation. Appl. Therm. Eng. 2021, 182, 116110. [Google Scholar] [CrossRef]
- Illán-Gómez, F.; Sena Cuevas, V.F.; García-Cascales, J.R.; Velasco, F.J.S. Experimental and numerical study of a CO2 water-to-water heat pump for hot water generation. Int. J. Refrig. 2021, 132, 30–44. [Google Scholar] [CrossRef]
- Nebot-Andrés, L.; Calleja-Anta, D.; Sánchez, D.; Cabello, R.; Llopis, R. Experimental assessment of dedicated and integrated mechanical subcooling systems vs parallel compression in transcritical CO2 refrigeration plants. Energ. Conv. Manag. 2022, 252, 115051. [Google Scholar] [CrossRef]
- Dai, B.; Zhao, X.; Liu, S.; Yang, Q.; Zhong, D.; Hao, Y.; Hao, Y. Energetic, exergetic and exergoeconomic assessment of transcritical CO2 reversible system combined with dedicated mechanical subcooling (DMS) for residential heating and cooling. Energy Convers. Manag. 2020, 209, 112594. [Google Scholar] [CrossRef]
- Dai, B.; Qi, H.; Liu, S.; Zhong, Z.; Li, H.; Song, M.; Ma, M.; Sun, Z. Environmental and economical analyses of transcritical CO2 heat pump combined with direct dedicated mechanical subcooling (DMS) for space heating in China. Energy Convers. Manag. 2019, 198, 111317. [Google Scholar] [CrossRef]
- Dai, B.; Qi, H.; Qi, H.; Liu, S.; Ma, M.; Zhong, Z.; Li, H.; Song, M.; Sun, Z. Evaluation of transcritical CO2 heat pump system integrated with mechanical subcooling by utilizing energy, exergy and economic methodologies for residential heating. Energy Convers. Manag. 2019, 192, 202–220. [Google Scholar] [CrossRef]
- Wang, G.-B.; Zhang, X.-R. Thermoeconomic optimization and comparison of the simple single-stage transcritical carbon dioxide vapor compression cycle with different subcooling methods for district heating and cooling. Energy Convers. Manag. 2019, 185, 740–757. [Google Scholar] [CrossRef]
- Yang, D.; Song, Y.; Cao, F.; Jin, L.; Wang, X. Theoretical and experimental investigation of a combined R134a and transcritical CO2 heat pump for space heating. Int. J. Refrig. 2016, 72, 156–170. [Google Scholar] [CrossRef]
- Qi, P.-C.; He, Y.-L.; Wang, X.-L.; Meng, X.-Z. Experimental investigation of the optimal heat rejection pressure for a transcritical CO2 heat pump water heater. Appl. Therm. Eng. 2013, 56, 120–125. [Google Scholar] [CrossRef]
- EN 14511-2; Air Conditioners, Liquid Chilling Packages and Heat Pumps for Space Heating and Cooling and Process Chillers, with Electrically Driven Compressors—Part 2: Test Conditions. European Committee for Standardization: Brussels, Belgium, 2018.
- ANSI/AHRI 540; Standard for Performance Rating of Positive Displacement Refrigerant Compressors and Compressor Units. ANSI/AHRI: Otawa, Canada, 2015; pp. 1–19.
- Dabiri, A.E.; Rice, C.K. Compressor-simulation model with corrections for the level of suction gas superheat. ASHRAE Trans. 1981, 87, 771–782. [Google Scholar]
- IMST-ART. A Simulation Tool to Assist the Selection, Design and Optimization of Refrigeration Equipment and Components; Instituto de Ingeniería Energética, Technical University of Valencia: Valencia, Spain, 2021; Available online: http://www.imst-art.com/ (accessed on 10 May 2022).
Equipment | Technical Info | |
---|---|---|
CO2 cycle | Evaporator | A = 0.552 m2 |
Compressor | ||
Gas cooler | A = 1.31 m2 | |
IHX | A = 0.082 m2 | |
Back Pressure Valve | kv = 0.042 m3·h−1 | |
Electronic Expansion Valve | kv = 0.18 m3·h−1 | |
Subcooler | A = 0.738 m2 | |
R1234yf cycle | Evaporator | |
Compressor | ||
Condenser | A = 0.322 m2 | |
Electronic Expansion Valve | kv = 0.164 m3·h−1 |
Configuration | Water Heating Configuration | IHX |
---|---|---|
CO2 cycle (Conf. A) | water heats up through gas cooler | X |
DMS CO2 cycle+ R1234yf cycle (Conf. B) | water heats up through condenser and gas cooler in series | - |
DMS CO2 cycle+ R1234yf cycle (Conf. C&C*) | water heats up through condenser and gas cooler in series with IHX located between evaporator and liquid receiver | X |
DMS CO2 cycle+ R1234yf cycle (Conf. D&D*) | water heats up through condenser and gas cooler in series with IHX between gas cooler and evaporator | X |
DMS CO2 cycle+ R1234yf cycle (Conf. E) | splitting strategy: water heats up through condenser and gas cooler in parallel | - |
DMS CO2 cycle+ R1234yf cycle (Conf. E*) | splitting strategy: water heats up through condenser and gas cooler in parallel | X |
Indirect DMS CO2 cycle+ R1234yf cycle (Conf. F) | splitting strategy: water heats up through condenser and evaporator + gas cooler in parallel | - |
Indirect DMS CO2 cycle+ R1234yf cycle (Conf. G) | splitting strategy: water heats up through condenser and evaporator + gas cooler in parallel | X |
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Illán-Gómez, F.; García-Cascales, J.R.; Sánchez-Velasco, F.J.; Otón-Martínez, R.A. Evaluation of the Use of Different Dedicated Mechanical Subcooling (DMS) Strategies in a Water Source Transcritical CO2 Heat Pump for Space Heating Applications. Clean Technol. 2022, 4, 1208-1226. https://doi.org/10.3390/cleantechnol4040074
Illán-Gómez F, García-Cascales JR, Sánchez-Velasco FJ, Otón-Martínez RA. Evaluation of the Use of Different Dedicated Mechanical Subcooling (DMS) Strategies in a Water Source Transcritical CO2 Heat Pump for Space Heating Applications. Clean Technologies. 2022; 4(4):1208-1226. https://doi.org/10.3390/cleantechnol4040074
Chicago/Turabian StyleIllán-Gómez, Fernando, José Ramón García-Cascales, Francisco Javier Sánchez-Velasco, and Ramón A. Otón-Martínez. 2022. "Evaluation of the Use of Different Dedicated Mechanical Subcooling (DMS) Strategies in a Water Source Transcritical CO2 Heat Pump for Space Heating Applications" Clean Technologies 4, no. 4: 1208-1226. https://doi.org/10.3390/cleantechnol4040074