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Special Issue "Waste Heat Recovery—Strategy and Practice"

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A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (30 June 2014)

Special Issue Editor

Guest Editor
Prof. Dr. Dieter Brüggemann (Website)

Director, Center of Energy Technology (ZET), University of Bayreuth, 95440 Bayreuth, Germany
Interests: thermodynamics; thermo-economy; thermal energy systems; waste heat recovery; organic Rankine cycle; thermal energy storage; IC engines, laser diagnostics

Special Issue Information

Dear Colleagues,

We know that energy conversion is typically accompanied by an undesired, but unavoidable, generation of waste heat. In particular industrial processes are emitting waste heat into the surroundings to an extent that its recovery and utilization could considerably contribute to the global reduction of fuel consumption and carbon dioxide emission. However, to achieve this objective one has to pay attention not only to technical feasibility, but also to economic reasonability. Both depend on the quantity of available waste heat and its quality, as defined by the temperature.

Bearing the importance of this subject in mind, you are invited to contribute a research paper to this Special Issue on “Waste Heat Recovery—Strategy and Practice”. It is dedicated to the progress in developing strategies for waste heat recovery and their implementation into practice. The contributions may include, but are not limited to, devices such as heat exchangers, heat pumps, heat pipes and thermal energy storage as well as heat-to-power conversion concepts based, for example, on the organic Rankine cycle.

Prof. Dr. Dieter Brüggemann
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs).

Keywords

  • waste heat recovery
  • thermal energy
  • heat exchanger
  • heat pumps
  • heat pipes
  • thermal energy storages
  • organic Rankine cycle

Published Papers (12 papers)

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Research

Open AccessArticle Naturally-Forced Slug Flow Expander for Application in a Waste-Heat Recovery Cycle
Energies 2014, 7(11), 7223-7244; doi:10.3390/en7117223
Received: 1 July 2014 / Revised: 20 October 2014 / Accepted: 21 October 2014 / Published: 10 November 2014
Cited by 1 | PDF Full-text (5448 KB) | HTML Full-text | XML Full-text
Abstract
This paper investigates a slug-flow expander (SFE) for conversion of high-pressure gas/vapor into kinetic energy of liquid slugs. The energy transfer from high-pressure to kinetic energy is quantified using thrust plate measurements. Non-dimensional thrust data is used to quantify performance by normalizing [...] Read more.
This paper investigates a slug-flow expander (SFE) for conversion of high-pressure gas/vapor into kinetic energy of liquid slugs. The energy transfer from high-pressure to kinetic energy is quantified using thrust plate measurements. Non-dimensional thrust data is used to quantify performance by normalizing measured thrust by thrust for the same water flow rate at zero air flow rate. A total of 13 expander configurations are investigated and geometries with the shortest cavity length and the smallest exit diameter are found to result in the largest non-dimensional thrust increase. Results show that thrust augmentation increases with the initiation of slug flow in the SFE. The analysis performed on the normalized thrust readings suggested that as the water and air flow were increased to critical conditions, the liquid slugs produced by the SFE augmented the thrust measurements. The final performance evaluation was based on linear regression of the normalized thrust measurements where slug flow was generated for each SFE architecture. Greater magnitudes of the slope from the linear regression indicated the propensity of the SFE to augment thrust. This analysis confirmed that for the SFE configurations over the range of values investigated, the SFE increased thrust up to three times its original value at no air flow. Given the inherent multiphase nature of the slug-flow expander, application to systems involving expansion of wetting fluids (water as part of a waste-heat recovery system) or air with water droplet formation (as part of a compressed-air energy storage system) could be considered. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
Open AccessArticle Modeling and Control of a Parallel Waste Heat Recovery System for Euro-VI Heavy-Duty Diesel Engines
Energies 2014, 7(10), 6571-6592; doi:10.3390/en7106571
Received: 30 June 2014 / Revised: 11 September 2014 / Accepted: 29 September 2014 / Published: 14 October 2014
Cited by 6 | PDF Full-text (1490 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the modeling and control of a waste heat recovery systemfor a Euro-VI heavy-duty truck engine. The considered waste heat recovery system consists of two parallel evaporators with expander and pumps mechanically coupled to the engine crankshaft. Compared to previous [...] Read more.
This paper presents the modeling and control of a waste heat recovery systemfor a Euro-VI heavy-duty truck engine. The considered waste heat recovery system consists of two parallel evaporators with expander and pumps mechanically coupled to the engine crankshaft. Compared to previous work, the waste heat recovery system modeling is improved by including evaporator models that combine the finite difference modeling approach with a moving boundary one. Over a specific cycle, the steady-state and dynamic temperature prediction accuracy improved on average by 2% and 7%. From a control design perspective, the objective is to maximize the waste heat recovery system output power.However, for safe system operation, the vapor state needs to be maintained before the expander under highly dynamic engine disturbances. To achieve this, a switching model predictive control strategy is developed. The proposed control strategy performance is demonstrated using the high-fidelity waste heat recovery system model subject to measured disturbances from an Euro-VI heavy-duty diesel engine. Simulations are performed usinga cold-start World Harmonized Transient cycle that covers typical urban, rural and highway driving conditions. The model predictive control strategy provides 15% more time in vaporand recovered thermal energy than a classical proportional-integral (PI) control strategy. In the case that the model is accurately known, the proposed control strategy performance can be improved by 10% in terms of time in vapor and recovered thermal energy. This is demonstrated with an offline nonlinear model predictive control strategy. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
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Open AccessArticle Development of Natural Gas Fired Combined Cycle Plant for Tri-Generation of Power, Cooling and Clean Water Using Waste Heat Recovery: Techno-Economic Analysis
Energies 2014, 7(10), 6358-6381; doi:10.3390/en7106358
Received: 30 June 2014 / Revised: 4 September 2014 / Accepted: 22 September 2014 / Published: 8 October 2014
Cited by 6 | PDF Full-text (2941 KB) | HTML Full-text | XML Full-text
Abstract
Tri-generation is one of the most efficient ways for maximizing the utilization of available energy. Utilization of waste heat (flue gases) liberated by the Al-Hamra gas turbine power plant is analyzed in this research work for simultaneous production of: (a) electricity by [...] Read more.
Tri-generation is one of the most efficient ways for maximizing the utilization of available energy. Utilization of waste heat (flue gases) liberated by the Al-Hamra gas turbine power plant is analyzed in this research work for simultaneous production of: (a) electricity by combining steam rankine cycle using heat recovery steam generator (HRSG); (b) clean water by air gap membrane distillation (AGMD) plant; and (c) cooling by single stage vapor absorption chiller (VAC). The flue gases liberated from the gas turbine power cycle is the prime source of energy for the tri-generation system. The heat recovered from condenser of steam cycle and excess heat available at the flue gases are utilized to drive cooling and desalination cycles which are optimized based on the cooling energy demands of the villas. Economic and environmental benefits of the tri-generation system in terms of cost savings and reduction in carbon emissions were analyzed. Energy efficiency of about 82%–85% is achieved by the tri-generation system compared to 50%–52% for combined cycles. Normalized carbon dioxide emission per MW·h is reduced by 51.5% by implementation of waste heat recovery tri-generation system. The tri-generation system has a payback period of 1.38 years with cumulative net present value of $66 million over the project life time. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
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Open AccessArticle Experimental Investigation of the Performance of a Hermetic Screw-Expander Organic Rankine Cycle
Energies 2014, 7(9), 6172-6185; doi:10.3390/en7096172
Received: 6 June 2014 / Revised: 15 August 2014 / Accepted: 22 September 2014 / Published: 23 September 2014
Cited by 5 | PDF Full-text (1514 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the authors experimentally investigate the performance of the organic Rankine cycle (ORC) and screw expander under the influence of supply pressure and pressure ratio over the expander. Three tests were performed with expander pressure ratios of 2.4–3.5, 3.0–4.6, and [...] Read more.
In this study, the authors experimentally investigate the performance of the organic Rankine cycle (ORC) and screw expander under the influence of supply pressure and pressure ratio over the expander. Three tests were performed with expander pressure ratios of 2.4–3.5, 3.0–4.6, and 3.3–6.1, which cover the over-expansion and under-expansion operating modes. The test results show a maximum expander isentropic efficiency of 72.4% and a relative cycle efficiency of 10.5% at an evaporation temperature of 101 °C and condensation temperature of 45 °C. At a given pressure ratio over the expander, a higher supply pressure to the expander causes a higher expander isentropic efficiency and higher cycle efficiency in the over-expansion mode. However, in the under-expansion mode, the higher supply pressure results in a lower expander isentropic efficiency and adversely affects the cycle efficiency. The results also show that under the condition of operation at a given pressure ratio, a higher supply pressure yields a larger power output owing to the increased mass flow rate at the higher supply pressure. The study results demonstrate that a screw-expander ORC can be operated with a wide range of heat sources and heat sinks with satisfactory cycle efficiency. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
Open AccessArticle Performance of Siloxane Mixtures in a High-Temperature Organic Rankine Cycle Considering the Heat Transfer Characteristics during Evaporation
Energies 2014, 7(9), 5548-5565; doi:10.3390/en7095548
Received: 30 June 2014 / Revised: 5 August 2014 / Accepted: 18 August 2014 / Published: 26 August 2014
Cited by 9 | PDF Full-text (2243 KB) | HTML Full-text | XML Full-text
Abstract
The application of the Organic Rankine Cycle to high temperature heat sources is investigated on the case study of waste heat recovery from a selected biogas plant. Two different modes of operation are distinguished: pure electric power and combined heat and power [...] Read more.
The application of the Organic Rankine Cycle to high temperature heat sources is investigated on the case study of waste heat recovery from a selected biogas plant. Two different modes of operation are distinguished: pure electric power and combined heat and power generation. The siloxanes hexamethyldisiloxane (MM) and octamethyltrisiloxane (MDM) are chosen as working fluids. Moreover, the effect of using mixtures of these components is analysed. Regarding pure electricity generation, process simulations using the simulation tool Aspen Plus show an increase in second law efficiency of 1.3% in case of 97/03 wt % MM/MDM-mixture, whereas for the combined heat and power mode a 60/40 wt % MM/MDM-mixture yields the highest efficiency with an increase of nearly 3% compared to most efficient pure fluid. Next to thermodynamic analysis, measurements of heat transfer coefficients of these siloxanes as well as their mixtures are conducted and Kandlikar’s correlation is chosen to describe the results. Based on that, heat exchanger areas for preheater and evaporator are calculated in order to check whether the poorer heat transfer characteristics of mixtures devalue their efficiency benefit due to increased heat transfer areas. Results show higher heat transfer areas of 0.9% and 14%, respectively, compared to MM. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
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Open AccessArticle Comparison and Impact of Waste Heat Recovery Technologies on Passenger Car Fuel Consumption in a Normalized Driving Cycle
Energies 2014, 7(8), 5273-5290; doi:10.3390/en7085273
Received: 19 June 2014 / Revised: 19 July 2014 / Accepted: 8 August 2014 / Published: 14 August 2014
Cited by 7 | PDF Full-text (529 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this article was to compare different waste heat recovery system technologies designed for automotive applications. A complete literature review is done and results in two comparative graphs. In the second part, simulation models are built and calibrated in order [...] Read more.
The purpose of this article was to compare different waste heat recovery system technologies designed for automotive applications. A complete literature review is done and results in two comparative graphs. In the second part, simulation models are built and calibrated in order to assess the fuel consumption reduction that can be achieved on a real driving cycle. The strength of this article is that the models are calibrated using actual data. Finally, those simulations results are analyzed and the Rankine cycle and turbocompound are the two most profitable solutions. However the simulations of the turbocompound shows its limitations because the impact on the exhaust pressure drop is not taken into account in the assessment of the car fuel consumption. Fuel reduction of up to 6% could be achieved, depending on the driving cycle and the waste heat recovery technology. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
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Open AccessArticle Study on the Characteristics of Expander Power Output Used for Offsetting Pumping Work Consumption in Organic Rankine Cycles
Energies 2014, 7(8), 4957-4971; doi:10.3390/en7084957
Received: 24 June 2014 / Revised: 25 July 2014 / Accepted: 28 July 2014 / Published: 31 July 2014
Cited by 3 | PDF Full-text (1283 KB) | HTML Full-text | XML Full-text
Abstract
The circulation pump in an organic Rankine cycle (ORC) increases the pressure of the liquid working fluid from low condensing pressure to high evaporating pressure, and the expander utilizes the pressure difference to generate work. A portion of the expander output power [...] Read more.
The circulation pump in an organic Rankine cycle (ORC) increases the pressure of the liquid working fluid from low condensing pressure to high evaporating pressure, and the expander utilizes the pressure difference to generate work. A portion of the expander output power is used to offset the consumed pumping work, and the rest of the expander power is exactly the net work produced by the ORC system. Because of the relatively great theoretical pumping work and very low efficiency of the circulation pump reported in previous papers, the characteristics of the expander power used for offsetting the pumping work need serious consideration. In particular, the present work examines those characteristics. It is found that the characteristics of the expander power used for offsetting the pumping work are satisfactory only under the condition that the working fluid absorbs sufficient heat in the evaporator and its specific volume at the evaporator outlet is larger than or equal to a threshold value. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
Open AccessArticle Performance Analysis of the Vehicle Diesel Engine-ORC Combined System Based on a Screw Expander
Energies 2014, 7(5), 3400-3419; doi:10.3390/en7053400
Received: 8 March 2014 / Revised: 28 April 2014 / Accepted: 13 May 2014 / Published: 22 May 2014
Cited by 6 | PDF Full-text (2366 KB) | HTML Full-text | XML Full-text
Abstract
To achieve energy saving and emission reduction for vehicle diesel engines, the organic Rankine cycle (ORC) was employed to recover waste heat from vehicle diesel engines, R245fa was used as ORC working fluid, and the resulting vehicle diesel engine-ORC combined system was [...] Read more.
To achieve energy saving and emission reduction for vehicle diesel engines, the organic Rankine cycle (ORC) was employed to recover waste heat from vehicle diesel engines, R245fa was used as ORC working fluid, and the resulting vehicle diesel engine-ORC combined system was presented. The variation law of engine exhaust energy rate under various operating conditions was obtained, and the running performances of the screw expander were introduced. Based on thermodynamic models and theoretical calculations, the running performance of the vehicle diesel engine-ORC combined system was analyzed under various engine operating condition scenarios. Four evaluation indexes were defined: engine thermal efficiency increasing ratio (ETEIR), waste heat recovery efficiency (WHRE), brake specific fuel consumption (BSFC) of the combined system, and improvement ratio of BSFC (IRBSFC). Results showed that when the diesel engine speed is 2200 r/min and diesel engine torque is 1200 N·m, the power output of the combined system reaches its maximum of approximately 308.6 kW, which is 28.6 kW higher than that of the diesel engine. ETEIR, WHRE, and IRBSFC all reach their maxima at 10.25%, 9.90%, and 9.30%, respectively. Compared with that of the diesel engine, the BSFC of the combined system is obviously improved under various engine operating conditions. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
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Open AccessArticle Preparation of Slag Wool by Integrated Waste-Heat Recovery and Resource Recycling of Molten Blast Furnace Slags: From Fundamental to Industrial Application
Energies 2014, 7(5), 3121-3135; doi:10.3390/en7053121
Received: 7 March 2014 / Revised: 26 April 2014 / Accepted: 4 May 2014 / Published: 9 May 2014
Cited by 6 | PDF Full-text (698 KB) | HTML Full-text | XML Full-text
Abstract
The present paper investigated the process of the slag wool fabrication using high temperature blast furnace (BF) slag modified by coal ash (CA). The liquidus temperature and viscosity of the slag system with different mass ratios of BF slag and CA were [...] Read more.
The present paper investigated the process of the slag wool fabrication using high temperature blast furnace (BF) slag modified by coal ash (CA). The liquidus temperature and viscosity of the slag system with different mass ratios of BF slag and CA were measured through an inner cylinder rotation method. The approximate mass ratio used to fabricate the slag wool was therefore determined and slag wool was then successfully prepared with a high-speed air injection method in the laboratory. The effect of mBF/m ratio, slag temperature for injection and air pressure on the preparation of slag wool was systematically investigated. The mechanical and thermal properties were also studied to confirm the long-term working conditions of the slag wool. An industry-scale slag wool production application was established. The energy consumption and the pollutant generation, were analyzed and compared with the traditional production method, which indicated a 70% reduction in energy consumption and a 90% pollution emission decrease. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
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Open AccessArticle Dynamic Response of a 50 kW Organic Rankine Cycle System in Association with Evaporators
Energies 2014, 7(4), 2436-2448; doi:10.3390/en7042436
Received: 29 January 2014 / Revised: 23 March 2014 / Accepted: 9 April 2014 / Published: 17 April 2014
Cited by 12 | PDF Full-text (334 KB) | HTML Full-text | XML Full-text
Abstract
The influences of various evaporators on the system responses of a 50 kW ORC system using R-245fa are investigated in this study. First the effect of the supplied hot water flowrate into the evaporator is examined and the exit superheat on the [...] Read more.
The influences of various evaporators on the system responses of a 50 kW ORC system using R-245fa are investigated in this study. First the effect of the supplied hot water flowrate into the evaporator is examined and the exit superheat on the system performance between plate and shell-and-tube evaporator is also reported. Test results show that the effect of hot water flowrate on the evaporator imposes a negligible effect on the transient response of the ORC system. These results prevail even for a 3.5-fold increase of the hot water flowrate and the system shows barely any change subject to this drastic hot water flowrate change. The effect of exit superheat on the ORC system depends on the type of the evaporator. For the plate evaporator, an exit superheat less than 10 °C may cause ORC system instability due to considerable liquid entrainment. To maintain a stable operation, the corresponding Jakob number of the plate heat evaporator must be above 0.07. On the other hand, by employing a shell and tube heat evaporator connected to the ORC system, no unstable oscillation of the ORC system is observed for exit superheats ranging from 0 to 17 °C. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
Open AccessArticle Effects of Degree of Superheat on the Running Performance of an Organic Rankine Cycle (ORC) Waste Heat Recovery System for Diesel Engines under Various Operating Conditions
Energies 2014, 7(4), 2123-2145; doi:10.3390/en7042123
Received: 26 January 2014 / Revised: 18 March 2014 / Accepted: 18 March 2014 / Published: 1 April 2014
Cited by 9 | PDF Full-text (2100 KB) | HTML Full-text | XML Full-text
Abstract
This study analyzed the variation law of engine exhaust energy under various operating conditions to improve the thermal efficiency and fuel economy of diesel engines. An organic Rankine cycle (ORC) waste heat recovery system with internal heat exchanger (IHE) was designed to [...] Read more.
This study analyzed the variation law of engine exhaust energy under various operating conditions to improve the thermal efficiency and fuel economy of diesel engines. An organic Rankine cycle (ORC) waste heat recovery system with internal heat exchanger (IHE) was designed to recover waste heat from the diesel engine exhaust. The zeotropic mixture R416A was used as the working fluid for the ORC. Three evaluation indexes were presented as follows: waste heat recovery efficiency (WHRE), engine thermal efficiency increasing ratio (ETEIR), and output energy density of working fluid (OEDWF). In terms of various operating conditions of the diesel engine, this study investigated the variation tendencies of the running performances of the ORC waste heat recovery system and the effects of the degree of superheat on the running performance of the ORC waste heat recovery system through theoretical calculations. The research findings showed that the net power output, WHRE, and ETEIR of the ORC waste heat recovery system reach their maxima when the degree of superheat is 40 K, engine speed is 2200 r/min, and engine torque is 1200 N·m. OEDWF gradually increases with the increase in the degree of superheat, which indicates that the required mass flow rate of R416A decreases for a certain net power output, thereby significantly decreasing the risk of environmental pollution. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
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Open AccessArticle Multi-Stage Control of Waste Heat Recovery from High Temperature Slags Based on Time Temperature Transformation Curves
Energies 2014, 7(3), 1673-1684; doi:10.3390/en7031673
Received: 20 January 2014 / Revised: 7 March 2014 / Accepted: 14 March 2014 / Published: 20 March 2014
Cited by 11 | PDF Full-text (980 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a significant method and a basic idea of waste heat recovery from high temperature slags based on Time Temperature Transformation (TTT) curves. Three samples with a fixed CaO/SiO2 ratio of 1.05 and different levels of Al2O [...] Read more.
This paper presents a significant method and a basic idea of waste heat recovery from high temperature slags based on Time Temperature Transformation (TTT) curves. Three samples with a fixed CaO/SiO2 ratio of 1.05 and different levels of Al2O3 were designed and isothermal experiments were performed using a Single Hot Thermocouple Technique (SHTT). The TTT curves established through SHTT experiments described well the variation of slag properties during isothermal processes. In this study, we propose a multi-stage control method for waste heat recovery from high temperature slags, in which the whole temperature range from 1500 °C to 25 °C was divided into three regions, i.e., Liquid region, Crystallization region and Solid region, based on the TTT curves. Accordingly, we put forward an industrial prototype plant for the purpose of waste heat recovery and the potential of waste heat recovery was then calculated. The multi-stage control method provided not only a significant prototype, but also a basic idea to simultaneously extract high quality waste heat and obtain glassy phases on high temperature slags, which may fill the gap between slag properties and practical waste heat recovery processes. Full article
(This article belongs to the Special Issue Waste Heat Recovery—Strategy and Practice)
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