Heat Source Temperature Research Articles

Thermodynamic performance of heat pump with R1234ze(E)/R1336mzz(E) binary refrigerant

In order to solve the temperature mismatch issue of cold and hot fluids in evaporation and condensation processes for heat pump system, binary refrigerant R1234ze(E)/R1336mzz is recommended in the present research due to its large temperature glide. Through theoretical analysis, multiple configurations under conditions of three different temperature heat sources (70/50 °C, 60/40 °C and 50/30 °C) and two different heat targets (steam above 100 °C and hot water with 70 °C) are constructed adopted Ebsilon code. The optimum mass proportion is obtained as 0.3/0.7 for R1234ze(E)/R1336mzz(E), because of its maximum temperature glide (can reach 21.52 °C) and excellent thermal performance (large COP, ECOP and exergy efficiency). COP of steam high temperature heat pump with R1234ze(E)(0.3)/R1336mzz(E)(0.7) binary refrigerant and the ratio of transferred heat of 110 °C condenser to all output heat (containing 110 °C and 100 °C steam intercooler and condensers) respectively increase up to 67.25% and 335.16% under some certain conditions, compared with that with pure R1336mzz(E). COP of hot water heat pump with R1234ze(E)(0.3)/R1336mzz(E)(0.7) binary refrigerant are respectively 10.31 and 6.89 under 60/40 °C and 50/30 °C heat source conditions, which greatly increases compared with that of heat pump with pure R1234ze(E) (6.67 and 5.03) and R1336mzz(E) (6.74 and 4.54). The present research may lay a foundation for binary refrigerant adoption to replace the scheme of multi-stage evaporator or multi-stage condenser, which could reduce the irreversible loss of phase change equipment and improve thermodynamic performance of heat pumps.

Parametric investigation and performance optimization of a MED-TVC desalination system based on 1-D ejector modeling

In recent decades, desalination has gained widespread recognition as a viable and reliable source of non-conventional fresh water. Desalination is the most expensive and energy-intensive method of water management. Researchers use various desalination and purification methods to provide fresh water to treat wastewater and seawater. This study conducted a parametric analysis and multi-objective optimization of a Three-effect Desalination with Thermal Vapour Compression (MED-TVC) system that provides the required energy with heat recovery. Influential system performance factors, including AR, Pc, Peff3, ΔTcond, and heat source temperature (THS), were evaluated using a comprehensive program built on energy analysis, exergy, and exergoeconomics. The findings demonstrated that increasing the recycled heat temperature from 120 to 180 °Cexerted a positive effect on freshwater production, energy efficiency, and Żtot, respectively. In addition, it was determined that the values of GOR, Żtot, and ṁd were 2.118, 3845 $/yr, and 30.33 g/s, respectively. Furthermore, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) approach was employed for multi-objective optimization to improve gained output ratio (GOR) and energy efficiency and lower costs relating to changes in the AR, Pc, and Peff3 parameters. The optimum points at THS = 160 °C were 7.524, 25.02 kPa, and 12.14 kPa, respectively. Moreover, the TVC system yielded the lowest cost (estimated at 35.33 $/yr), and the second effect yielded the highest cost (calculated at 562.6 $/yr). Finally, calculated values for GOR, Żtot, and ṁd were 2.18, 3845 $/yr, and 30.33 g/s, respectively.

Flash evaporation strategy of organic Rankine cycle for geothermal power performance enhancement: A case study

The performance of organic Rankine cycle (ORC) is poor due to the high irreversible losses in evaporator. To improve system performance, organic Rankine single flash cycle (ORSFC) and organic Rankine double flash cycle (ORDFC) are proposed, in which the traditional evaporation process is split into incomplete evaporation and flash evaporation. Thermal and exergetic efficiencies are taken as the objective functions, and the effects of the related operating parameters and the number of the flash stage on the thermodynamic performance of the system is conducted. The results show that for the ORSFC and ORDFC, in the direction of the rise of the heat source temperature, the net power output increases, the optimal evaporation temperature and flash temperature corresponding to different performance criteria also gradually increase. Besides, the dryness of the evaporator outlet is inversely proportional to the net power output, while it is directly proportional to the system efficiencies. When the dryness increases by 0.1, the net power output of the ORSFC and ORDFC decreases by an average of 148.5 kW, the thermal efficiency and exergetic efficiency of the ORSFC and ORDFC increase by an average of 0.56% and 1.37%, respectively. Moreover, with the flash stages increase, the performance criteria are improved at different magnitude. When a specific thermodynamic parameter is optimized, the ORDFC always obtains the best value for this parameter.

Application of Particle Image Velocimetry and Computational Fluid Dynamics Methods for Analysis of Natural Convection over a Horizontal Heating Source

The objective of this article is to address the challenges associated with visualizing air flow over a heating source in an open laboratory environment. The study uses a combination of experimental visualization and numerical simulation techniques to generate a 3D model of the air flow and heat transfer between the heating source and the environment via natural convection. The Particle Image Velocimetry method is used to experimentally visualize the air flow, which is known for its benefits of high speed and accuracy, and for its ability to avoid disturbing the flow of the fluid being investigated. The data obtained from this experimental method are used as input for numerical simulations using the Ansys Fluent program. The numerical simulations identify air vortices and other elements that disrupt the airflow in the laboratory environment. The resulting 3D model accurately represents the actual situation in the laboratory and could be further optimized by adjusting parameters such as the output of the heater and the heating source temperature. These parameters play a crucial role in ensuring thermal comfort in the laboratory environment, which is of utmost importance for user comfort. In conclusion, the study provides valuable insights into the visualization of air flow over a heating source and demonstrates the effectiveness of combining experimental and numerical simulation techniques to generate accurate 3D models of air flow and heat transfer.

Low-grade thermal energy utilization through using organic Rankine cycle system and R1233zd(E) at different heat source temperatures

The organic Rankine cycle (ORC) is a promising thermal-electric conversion technology for low-grade thermal energy utilization, however, its performance is significantly varied by the heat source condition. In this study, a compact ORC system using R1233zd(E) was built in Harbin, China for low-grade thermal energy utilization, and the thermal performances of the system at different heat source temperatures (HST, 80, 100, and 120 °C) and heat-source mass flow rates (mhs, 0.011 ∼ 0.346 kg/s) were investigated and presented. The results showed that the heat source conditions (HST and mhs) primarily influenced the ideal bubble point temerature difference (BPTD), outlet pressure, and super-heating degree (SHD) of the evaporator. With the increases in HSTs and mhs, the net output power, thermal efficiency, electricity generation and electricity generation efficiency varied in the ranges of 0.04 ∼ 0.77 kW and 0.9 % ∼ 7.1 %, 0.02 ∼ 0.51 kW and 0.5 % ∼ 4.7 %, respectively. The biggest thermal efficiency (7.1 %) and electricity generation efficiency (4.7 %) of the ORC were obtained at the HST of 120 °C, mhs of 0.09 kg/s. The results also showed that the disadvantages of low-temperature thermal energy could be compensated by improving the mhs, providing more possibilities for the efficient utilization of ORC systems driven by low-grade thermal energies.

Experimental study on pressure-enhanced close contact melting with PCMs for stable temperature control of high heat flux electronic devices

Phase change material (PCM) demonstrates great potential for the thermal management of electronic devices. However, stable temperature control is hardly achieved because of the moving melt front during the phase change process. This study presents the pressure-enhanced close contact melting method for PCM, from the application aspect via visualization study. The overheated liquid PCM can be rapidly removed from the heat source, thus achieving stable temperature control for electronic device when operating under high heat flux. The transient performances of paraffin and low melting point alloy are evaluated, respectively, under various heat loads and pressures. It is recognized from the visualization test that the conventional PCM-based and metal foam-enhanced heat sinks fail to achieve stable temperature control since the continuously elevated liquid thickness between melt front and heat source results in increasing thermal resistance. However, the pressure-enhanced close contact melting method might continuously squeeze melted liquid, thus promoting the contact of melt front with the heat source. The effects of applied pressures and heat loads on the transient thermal management performance over time are virtually investigated. As the result, the surface temperature of heat source can be stabilized around the melting point of PCM. When applying the pressure of 2250 Pa, the thermal resistance can be minimized to lower than 10−4 K·m2·W−1. It is also noted that the thermal management performance remains unchanged when the pressure exceeds 1250 Pa.

A Review of Numerical Simulation of Laser-Arc Hybrid Welding.

Laser-arc hybrid welding (LAHW) is known to achieve more stable processes, better mechanical properties, and greater adaptability through the synergy of a laser and an arc. Numerical simulations play a crucial role in deepening our understanding of this interaction mechanism. In this paper, we review the current work on numerical simulations of LAHW, including heat source selection laws, temperature field, flow field, and stress field results. We also discuss the influence of laser-arc interaction on weld defects and mechanical properties and provide suggestions for the development of numerical simulations of LAHW.

Experimental study of an organic Rankine cycle with a variable-rotational-speed scroll expander at various heat source temperatures

Experimental study of an organic Rankine cycle with a variable-rotational-speed scroll expander at various heat source temperatures

Study and application of the shift-temperature of heating fluid for zeotropic mixtures in organic Rankine cycle

The theoretical formulations of the shift-temperature of the heating fluid for zeotropic mixtures (Tshift) were derived when the pinch point was located at the evaporating bubble point and the working fluid inlet of the evaporator, respectively, which were applicable to dry, wet, and isentropic zeotropic mixtures. Tshift was corrected by the impact factor analysis and calculated exactly using the Dragonfly algorithm. The optimal zeotropic mixture was matched by comparing the heat source temperature(Tg, in) and Tshift. The results indicate that Tshift is a property of every zeotropic mixture and is related to the critical temperature, the evaporation bubble point temperature, and the condensation dew point temperature. When the pinch point is at the evaporation bubble point, the zeotropic mixture with Tshift lower than Tg, in is selected and then combined with the thermal efficiency for a comprehensive evaluation. When the pinch point is at the working fluid inlet of the evaporator, Tshift is also affected by the pinch point temperature difference and the temperature glide of the condensation process, Tshift is significantly lower than Tg, in, all zeotropic mixtures are applied. Among the matched zeotropic mixtures, R227ea/R22 with the lowest Tshift has the best thermal performance in the ORC system.

A comparative performance analysis, working fluid selection, and machine learning optimization of ORC systems driven by geothermal energy

Geothermal-energy-based desalination plants that utilize reverse osmosis (RO) are evaluated in detail with the aim of converting the thermal energy of geothermal flow into electricity based on three configurations of the organic Rankine cycle (ORC). These systems include basic ORC, parallel ORCs, and series ORCs. The performance of the proposed systems is evaluated by developing thermodynamic and economic models. A parametric study is conducted to assess the impact of main design parameters on the performance. Moreover, a multi-objective optimization procedure is implemented, by coupling the genetic algorithm (GA) with an artificial neural network (ANN), to identify optimal cycle configuration and working fluid(s) under three different heat source temperatures. For a specific geothermal temperature (135 °C), the highest exergy efficiency in the basic scheme is obtained by R1233zd (E), while ammonia yields maximum power generation. For parallel configuration, irrespective of the heat source temperature, the combination of R1233zd (E)-Ethane always leads to the highest exergy efficiency, while comparison results at 135 °C indicate that the combination favored by power generation is R1234ze (Z)-Ethane. For the series configuration, optimization results under the heat source temperature of 135 °C indicate that the ammonia-R1234ze (Z) combination is a suitable candidate under the economic objective, while ammonia-ammonia is recommended as the preferred choice thermodynamically. In addition, comparing the optimization results of the parallel configuration with the basic design reveal considerable improvements of about 150% and 60% in power generation and water production, respectively. The same comparison between series and basic configurations revealed an improvement of about 30% in power generation.

Energetic Analysis of Low Global Warming Potential Refrigerants as Substitutes for R410A and R134a in Ground-Source Heat Pumps

The European building sector is responsible for approximately 40% of total energy consumption and for 36% of greenhouse gas emissions. Identifying technological solutions capable of reducing energy consumption and greenhouse gas emissions is one of the main objectives of the European Commission. Ground source heat pumps (GSHPs) are of particular interest for this purpose, promising a considerable reduction in greenhouse gas emissions of HVAC systems. This paper reports the results of the energetic analysis carried out within the EU research project GEO4CIVHIC about the performance of geothermal heat pumps working with low-GWP refrigerants as alternatives for R134a and R410A. The work has been carried out through computer simulations based on base and regenerative reverse cycles. Several heat sink and heat source temperature conditions have been considered in order to evaluate the GSHPs’ performance in the whole range of real conditions that can be found in Europe. Particular attention has been paid to the evaluation of compression isentropic efficiency and its influence on the overall cycle performance when dealing with steady-state heat pump simulations. To do so, five different scenarios of isentropic efficiency calculation have been studied and discussed.

Extremum seeking control for real-time optimization of high temperature heat pump systems incorporating vapor injection

In order to minimize the power consumption of a vapor-injected high temperature heat pump system with R245fa as refrigerant, a control strategy, namely Extremum seeking control, is proposed. It can implement real-time model-free optimization control of plants with concave and convex properties. Modelica-based dynamic simulation model of the proposed system is developed. The Newton-based Extremum seeking control is used to optimize the intermediate pressure of the proposed system to obtain the minimum power consumption of the compressor at a fixed heating capacity (200 kW). The adopted ESC strategy requires four measured quantities, namely, injection pressure, condenser outlet water temperature, evaporator outlet superheat and compressor power consumption, to achieve optimal control of the system in real time. Two operation scenarios are simulated: stable and freely variable heat source temperature. For both scenarios, the condenser outlet water temperature was set to 140 °C. The simulation results show that at stable heat source temperature, the power consumption is reduced by 5.2% and the COP is increased by 7.7% compared to a fixed initial intermediate pressure. Under the free-variable heat source condition, the power consumption can be reduced by up to 5 kW compared to a constant input. A total of 283 kWh of power was saved during the 48 h simulation. Thus, the Newton-based extremum seeking control strategy can optimize the intermediate pressure to achieve the minimum power consumption while maintaining excellent transient performance, and demonstrate the superiority of the ESC strategy for real-time optimization..

Energy and exergy analyses of a hybrid adsorption refrigeration system for simultaneous production of cold water and dry air

Current adsorption refrigeration systems are limited by dehumidification methods and produce either cold water or cold dry air. The single cooling product greatly hinders their application into situations where multiple cooling outputs are needed. In order to address this issue, this paper introduces a hybrid adsorption refrigeration system using efficient desiccant coated heat exchangers to provide both cold water and dry air via the deep utilization of input heat sources. In this study, the performance of the hybrid system is experimentally investigated from a combined perspective of energy and exergy. Results show that the hybrid system can simultaneously output cold water and dry air with a heat source of 50–80 °C. A low-temperature cooling water is beneficial to system performance, while an optimum input hot water temperature exists. At a coolant-side temperature of 25 °C, the COP reaches its maximum of 0.238 under a heat source temperature of 60 °C, and the highest exergetic efficiency is quantified as 13.9% when powered by 50 °C hot water. Increasing inlet air temperature or relative humidity facilitates the COP improvement but has a negligible effect on the exergetic efficiency. In comparison with a traditional adsorption air conditioning system, the hybrid system has a wider range of input hot water temperatures and is more advantageous in terms of cooling exergy and exergetic efficiency. This hybrid system firstly enables adsorption refrigeration to export dual cooling products of cold water and dry air, which is expected to extend adsorption refrigeration into fully automatic industrial fields.

Experimental and computational study on utilising graphene oxide for adsorption cooling and water desalination

The adsorbent material’s thermal and sorption characteristics are the critical criteria that affect the adsorption systems’ overall performance. Therefore, this paper experimentally and computationally studies the utilisation of graphene oxide of a few atomic layers as a parent adsorbent material owing to its reported high thermal performance potential. Graphene oxide performance was benchmarked against the widely investigated silica gel adsorbent, emphasising adsorption cooling cum desalination application as the most needed to address the lack of sustainable cooling and clean water scarcity. Quantitative and qualitative analyses were undertaken to determine the influence of the evaporator temperature, cycle time and heat source temperature on the material and system levels. The results showed that graphene oxide enhances thermal performance by 44% compared to silica gel and adsorption by up to 57%. Furthermore, graphene oxide, compared to silica gel as a parent adsorbent, enhanced the system’s specific daily water production by up to 44.4%, the specific cooling power by up to 29.5%, the coefficient of performance by up to 17.2% and the exergy efficiency by up to 15.8%.

Multi-variable extremum seeking control for high temperature heat pump system incorporating double refrigerant injection

The use of refrigerant injection technology to enhance the heating efficiency of heat pumps with larger temperature lifts is becoming more common. Heat pumps with double refrigerant injection loops have better energy efficiency than traditional ones with single refrigerant injection loops. A multi-variable extremum seeking control (ESC) strategy for a high-temperature heat pump system with double refrigerant injection technology is proposed in this study. A Modelica-based dynamic simulation model of the considering system is established in Dymola, and a co-simulation with the proposed ESC strategy is built to validate the effectiveness of this control strategy to minimize power consumption. The strategy uses compressor power consumption as the feedback. The effective throttling area of the upper and lower EEVs is adjusted by a PI controller to manipulate the low and high-pressure vapor injection pressures. Three scenarios were simulated for control: stable, step curve, and freely variable heat source temperature conditions. The simulation results demonstrate that the multi-variable ESC has excellent convergence performance and confirm its effectiveness in searching for the optimal operating point.

Impacts of the internal heat recovery scheme on the performance of an adsorption heat transformer cycle for temperature upgrade

Adsorption heat transformer (AHT) cycles, unlike adsorption cooling cycles, upgrade the heat source to a higher temperature. Despite the renewed interest in the AHT cycles, its performance enhancement schemes along with their impacts are yet to be explored extensively. Heat and mass recovery schemes on the adsorption cooling/heating cycles have been extensively studied. However, AHT cycles are fundamentally different from those cycles since the AHT cycles employ isothermal-adiabtic processes. Thus, similar impacts of the heat and mass recovery scheme as in the cooling/heating cycles cannot be expected in AHT cycles. Therefore, the impacts and limitations of the internal heat recovery scheme on the AHT cycle are investigated in the current study. The heat recovery scheme aims to minimize the requisite uptake consumption for preheating the adsorber bed by recovering the sensible heat between two adsorber beds having different temperatures. This sensible heat exchange is modeled using modified energy-balance equations to capture the non-linearity of the adsorption process. The preheating uptake loss decreases from 0.014 kg/kg to 0.007 kg/kg at the heat source-heat supply temperature combination of 60 °C–80 °C due to the maximum possible heat recovery in the AHT cycle. As a result of the reduced preheating uptake loss, approximately 5% and 10% increase in the useful heat ratio and exergy efficiency of the AHT cycle, respectively are obtained. This modified AHT cycle further improves the performance ratio of the hybrid AHT-MED (multi-effect distillation) system from 4.6 to 4.9 at the heat source temperature of 58 °C. Furthermore, a parametric analysis of the cycle's performance metrics has been conducted for various degrees of heat recovery, representing the effect of realistic heat exchanger effectiveness during the recovery process. This study will help propel the theoretical development of the adsorption-based thermodynamic systems.

New configurations of absorption heat transformer and refrigeration combined system for low-temperature cooling driven by low-grade heat

A significant proportion of industrial waste heat and renewable energy is low-grade with temperatures below 100 °C, which can hardly drive the conventional absorption refrigeration systems for producing cooling below 0 °C. To solve this problem, an absorption heat transformer, whose absorber is combined with the generator of the absorption refrigeration system, is introduced to increase the temperature of the low-grade heat source to drive the absorption refrigeration system. Temperature matching between the two sub-systems and between the heat source and the combined system determines the performance of the combined system. Hence, new configurations and continuous-temperature-changing processes are proposed and numerically studied. Results show that the system performance improves significantly when continuous-temperature-changing processes are introduced, and the utilization temperature span of heat source and the refrigeration capacity increase by 80 % and 108 %, respectively. Moreover, the continuous-temperature-changing absorption-generation process is investigated by dividing into 8 sections, and it is found that the process achieves optimal performance, when the absorption side only has adiabatic and absorption sections, and the generation side only has adiabatic and generation sections. Results indicate that the proposed system shows great potential to harvest low-grade heat at 80 °C, and produce refrigeration capacity below −15 °C.

Dynamic compact thermal models for skin temperature prediction of portable electronic devices based on convolution and fitting methods

In most portable electronic devices, besides the temperature of multiple heat sources, i.e. junction temperature, the temperature of the enclosure, i.e. skin temperature, should also be controlled to protect the user experience. Thus, generating the device-level compact thermal model for predicting the skin temperature will not only improve the efficiency of early-stage thermal design but also help to develop the model-based temperature control strategy. However, most of the existing modeling methods mainly focus on predicting the junction temperature. In this paper, the dynamic compact thermal models of two portable electronic devices, including a smartphone and laptop, are first generated based on the convolution method. Under the assumption of linear time-invariant (LTI) systems, the skin temperature of the two test devices could be fast calculated once the step response of each heat source is obtained. The results show that compared to the computational fluid dynamics (CFD) model generated in ANSYS Icepak, the transient deviation of the convolution-based model is within 5%. Then, a linear fitting model is proposed to real-time predict the skin temperature of laptops. Both the experimental and simulation results demonstrate that once the scale factors are trained, the linear fitting model could accurately real-time predict the skin temperature after 60s. The maximum transient deviation in the experiment and simulation are 4% and 7% respectively. The results indicate that the proposed modeling method has tremendous potential for both thermal design and control optimization.

Thermo-economic assessment of sub-ambient temperature pumped-thermal electricity storage integrated with external heat sources

Thermally integrated pumped-thermal electricity storage (TI-PTES) offers the opportunity to store electricity as thermal exergy at a large scale, and existing studies are primarily focused on TI-PTES systems based on high-temperature thermal energy storage. This paper presents a thermo-economic analysis of a “cold TI-PTES” system which converts electricity into cold energy using a vapor compression refrigeration (VCR) unit and stores it at sub-ambient temperatures during the charging process, and generates electricity by using an organic Rankine cycle (ORC) working between the sub-ambient temperature and an external low-grade heat source during the discharging process. The effects of key parameters, i.e., mass flowrate and temperature of the storage medium, ORC evaporation temperature, component efficiencies, and pinch-point temperature differences, on the system performance are evaluated based on a whole-system thermo-economic model. The results reveal that the roundtrip efficiency and levelized cost of storage (LCOS) of the system increases while the electrical energy storage capacity decreases as the temperatures of the two cold storage tanks approach each other. When the temperature of the cold storage tank 1 rises from 1 °C to 8 °C while the cold storage tank 2 remains as 13 °C, there is an increase of 25% and 20% in the roundtrip efficiency and LCOS respectively while the energy storage capacity decreases by 69%. A roundtrip efficiency of 0.74 and LCOS of 0.32 $/kWh are achieved with a heat source temperature of 85 °C, using a mass flowrate and temperature of the cold storage medium of 50 kg/s and 1 °C. Furthermore, any change in cold storage medium mass flowrate changes both electrical energy storage capacity and power output by the same proportions. With a continuous high-flowrate external heat source, the LCOS can be as low as 0.17 $/kWh. By providing sufficient heat from an external heat source, the proposed system possesses a high potential for medium-to-large scale energy storage with a unique hybrid nature for electricity storage and thermal integration.

Experimental investigations on the performance of a thermo-mechanical refrigeration system utilizing ultra-low temperature waste heat sources

Experimental studies that investigate the utilization of ultra-low temperature (between 48 °C and 120 °C) waste heat, which forms 25 % of the global unrecovered waste heat, to drive thermal cooling systems are rare. Thus, this study fills a significant gap in the literature by (i) experimentally evaluating the performance of a new full-scale thermo-mechanical refrigeration (TMR) system at ultra-low temperatures ranging from 50 °C to 85 °C, (ii) characterizing its operation with different commercial refrigerants, and (iii) identifying optimal operating conditions and working fluids for the investigated TMR system. An organic Rankine cycle (ORC), vapor compression cycle (VCC), and expander-compressor unit (ECU) make up the TMR system. To ensure its efficient operation, flexibility, and reliability, a full-scale ECU-based TMR system with a design capacity of 1 kW at a heat source temperature of 85 °C is built and put through a series of tests. Furthermore, the TMR system is tested with different commercial refrigerants (R134a, R410A, R407C) over a wide range of operating conditions of the power loop. The results reveal that the ECU-based TMR system can work with ultra-low temperatures of 65 °C with an energy efficiency of 5.92 % and COP of 2.36, for the ORC and VCC, respectively. At a heat source temperature of 85 °C, a condenser water temperature of 15 °C, and an evaporator water temperature of 33 °C, the energy efficiency of the ORC and COP of the VCC are increased to 9.85 % and 3.99, respectively. For the cooling quality, the TMR system shows a minimum evaporator temperature of −10 °C using R134a in both the power and cooling loop, which is improved to lower than −20 °C by using R407C in the cooling loop. The results presented herein will be beneficial to the development, design, and optimization of refrigeration and power systems that utilize low-temperature waste heat.