Maximum Coefficient Of Performance Research Articles

High Performance BiSbTe Alloy for Superior Thermoelectric Cooling

AbstractAt present, the weak thermoelectric and mechanical performance of zone‐melting bismuth telluride alloys cannot support the further improvement of cooling and processing performance of semiconductor refrigeration devices. Here, MnO2 is added into high‐strength Bi0.4Sb1.6Te3 prepared by ball milling method to optimize its thermoelectric transport properties. Via in situ reaction, Sb2O3 nano‐precipitates are formed in the matrix, which also leads to the surplus of Te element. As results, the donor‐like effect is suppressed, thereby increasing carrier concentration and power factor. Besides, volatilization of Te‐rich phases during sintering leaves plentiful nanopores, which together with Sb2O3 nano‐precipitates significantly decrease the lattice thermal conductivity. Eventually, the maximum ZT reaches 1.43 at 75 °C for the Bi0.4Sb1.6Te3+0.01MnO2 sample. On this basis, a 31‐pairs module made of the material and commercial n‐type BiTeSe produces large temperature differences (ΔT) of 70.1, 80.8, and 89.4 K at the hot‐side temperature (Th) of 300, 325, and 350 K respectively, which are highly competitive. The maximum coefficient of performance of 8.6 and cooling capacity of 7 W are achieved when Th is set as 325 K. This excellent progress will promote the further development of bismuth telluride refrigeration modules.

Performance analysis of heat pipe-cooled two-stage thermoelectric air conditioner

A detailed model of heat pipe-cooled two-stage thermoelectric (TE) air conditioner is established. The performance is analysed comprehensively including the cooling power, coefficient of performance (COP), thermodynamic perfectibility and extreme temperature difference. The influences of key parameters including working current, distribution ratio of TE elements and heat pipe parameters are analysed by numerical simulation. The working current and the TE element number ratio are optimized for the maximum cooling power and the maximum COP respectively. The influences of the cross-sectional area, the length of the TE element and the temperature difference on the optimal variables and optimal performance is obtained. The results show the refrigeration performance of the TE air conditioner can be effectively improved by heat pipe cooling. The two-stage mode can effectively improve the refrigeration temperature difference. The extreme temperature difference can be improved from 60 K to 110 K.

Enhancing the Energy Efficiency—COP of the Heat Pump Heating System by Energy Optimization and a Case Study

This article deals with the degrees of freedom and possible optimums, specifically with the energy optimums of the heat pump heating system. The authors developed an multi objective optimization procedure that allows for the determination of the optimal motor power for the circulation and well pumps in order to achieve the maximum COP. Upon selecting the type and size of the water-to-water heat pump, based on the heating demand of the buildings, the proper power of the circulation and well pumps must be determined. There are several procedures used for determining the pump’s power. However, none of those methods ensures the optimum power, i.e., the maximum coefficient of performance, COP of the heating system. In this study, a multi objective analytical-numerical dimensioning procedure was developed for the determination of the optimal mass flow rate of warm and well water. Based on the flow rate values, the optimum power of the circulation and well pumps can be calculated. Due to the wide scope of the topic, the application of the optimization procedure is presented in a case study, but only for determining the optimum power of the circulation pump. The validity of the procedure was confirmed by measurements. The results obtained with the optimization showed that through the energy optimization of the circulation pump power, the COP of the system increased by 5.34%.

Experimental and numerical study on a novel fanless air-to-air solar thermoelectric refrigerator equipped with boosted heat exchanger

Peltier cooling systems are generally small, portable and simple in operating principle compared to conventional vapor compression cooling systems. For these reasons, Peltier cooling systems are proposed widely to use in the field. In studies on Peltier coolers presented in the literature, equipment such as pumps and fans is used and this causes noise and vibration. In order to resolve these problems and negative effects, a cooling system was designed and manufactured using completely motionless elements. Additionally, the electricity energy need of this thermoelectric cooling chamber is fully met by solar energy. This study was investigated both experimentally and numerically by using computational fluid dynamics (CFD) methods. By designing a special heat exchanger in the produced air-to-air cooler system, it has been proven that, the Peltier system can work effectively without the need for any elements such as fans. Then the effects of the voltage values applied to the system and the number of Peltier modules have been investigated. The experiments were carried out at 4 different voltage values (1.5, 2.0, 2.5 and 3.0 V) and in 3 different Peltier numbers (1, 3 and 5) in consecutive connections. According to the obtained results, the most suitable situation for reducing the temperature of the cooling chamber were obtained as the voltage was at a maximum of 3 V and the Peltier number was maximum (5 Peltiers mode), where the internal temperature of the cooling chamber decreased to 11.28 °C. It was observed that, the coefficient of performance (COP) values decreased over time in all experiments. Considering the data taken at the beginning of the experiments, the maximum COP value was obtained as 0.04 when 1 Peltier and 1.5 V voltage were applied.

Performance Analysis of Low-Capacity Water–LiBr Absorption–Cooling Systems Using Geothermal Heat-Sinks in Hot Climates

This paper addresses the use of a geothermal heat-sink to remove the heat released in domestic-sized single and double-effect water–LiBr absorption chillers operating in hot climates. This study is the continuation of a previous work, which demonstrated the operational constraints of these absorption chillers working in hot Algerian climate-zones. After localizing the non-operation zones for both systems, the thermo-physical properties of the soil at several depths are investigated for the implementation of the underground heat-exchanger. This heat-exchanger is connected to the condenser and the absorber of both systems, to supply cooling water at inlet temperatures of 33 °C in hot climate conditions, with ambient temperatures varying from 38 °C to 42 °C. The results show a steady operation for both absorption chillers in climate conditions which had not previously allowed the two systems to operate in water or air-cooled modes. A maximum coefficient of performance of 0.76 and 1.25 is obtained for single- and double-effect absorption cycles, respectively, with chilled water at 7 °C. The underground-tube length required is between 4.5 and 18 m, depending on the absorption-cycle configuration and the temperature of the chilled water.

High-performance polymer-based regenerative elastocaloric cooler

Alternative methods of refrigeration are critical for performance optimization and environ- mental sustainability. Prototype systems using caloric materials have shown the advantages of a high coefficient of performance (COP) and low global warming potential. Elastocaloric elastomers can meet ongoing needs, but their implementation in functional heat pumps or coolers remains challenging due to their requirement for a large deformation and low thermal conductivity. Moreover, a scalable design is required to achieve high cooling power. As a leap forward for the use of polymers in larger scale caloric devices, we developed experimental elastocaloric polymer coolers with two different geometries using natural rubber tubes. We confirmed that a suitable geometry partially compensated for the low thermal conductivity and led to performances comparable to those of other caloric devices. Several operating conditions were tested to determine the optimal temperature span, cooling power, and COP for both device geometries. Under a specific operating condition, one of the prototypes exhibited a maximum temperature span > 8 K, a maximum COP of 6, and an output cooling power of 1.5 W; this power outperforms other prototypes based on polymers or ceramics. The parallelization of rubber tubes will facilitate realistic elastocaloric polymer coolers on a larger scale.

Heat pump assisted open three-phase sorption thermal battery for efficient heat storage

Open three-phase sorption thermal battery has recently received particular attention for its high energy storage density. Meanwhile, air source heat pump can be considered a potential heat source for open three-phase sorption thermal battery due to its broad applicability and high energy efficiency. However, research on the intergration of these two systems are rarely reported. A heat pump assisted sorption thermal batttery is proposed and evaluated based on a general thermodynamic analysis for charging process. Three indicators are targeted in terms of coefficient of performance (COP), energy storage rate and energy storage density. Results show that system characteristics present three different patterns, i.e., liquid desorption, crystallization and dehydration stages. When ambient condition is 20 °C and 60% RH, the maximum system average COP is 7.53, the corresponding charge temperature is 40 °C and end-state sorption capacity is 2.33 g/g. The optimal charging condition for comprehensive performance index is greatly affected by the weights of basic indicators. When the weight of energy storage density is dominating, three-phase sorption performs better. Within the range of this study, the optimal sorbent end state locates on either liquid desorption stage or dehydration line.

Performance analysis of a new transcritical R744 refrigeration cycle with expander-mechanical overheating

• ·A new model of supercritical R744 refrigeration system is proposed. • ·R744/R41 (25/75) mixed refrigerant is used in the coupling system. • ·Comparing with conventional system, new system can reduce the optimal pressure. • ·Comparing with conventional system, new system can increase the system COP. • ·The influence of superheat on system performance is analyzed emphatically. In this paper, a transcritical R744 refrigeration cycle with expander mechanical overheating coupling is proposed. When the reasonable superheat and the pressure difference front and rear of expander are selected, the coefficient of performance of R744 refrigeration cycle can be significantly improved and the discharge pressure can be reduced. Compared with the base R744 refrigeration cycle and the R744 refrigeration cycle with expander, the coefficient of performance of the expander mechanical overheating coupling transcritical R744 refrigeration cycle can increase by 20.17% and 10.59%. In addition, in the expander mechanical overheating coupled transcritical R744 refrigeration cycle system, with the increase of superheat, the minimum optimal pressure can be reduced by 8.63% and the maximum coefficient of performance can be increased by 131.17%. With the increase of pressure difference front and rear of expander, the minimum optimal pressure can be reduced by 6.14% and the maximum coefficient of performance can be increased by 72.19%. Therefore, from the perspective of improving the comprehensive performance of the system, the superheat should be properly increased, supplemented by the pressure difference front and rear of expander, which can not only reasonably improve the comprehensive performance of the system, but also reduce the design difficulty of the expander.

Thermochemical energy storage using coupled metal hydride beds of Mg-LaNi5 composites and LaNi5 based hydrides for concentrated solar power plants

• A MHTES system is proposed for CSP plant application. • Energy storage and recovery temperatures are estimated. • PCIs of Mg based composites and LaNi 5 based alloys are measured. • Reaction enthalpy and entropy are evaluated using van’t Hoff equation. • The performance of the MHTES system is analyzed thermodynamically. • The effect of operating temperatures on the performance of the MHTES is studied. Thermochemical energy storage based on coupled hydride beds is an attractive option for Concentrated Solar Power plant applications due to its efficient long term and high energy storage density. In the coupled system, a high temperature metal hydride (HTMH) bed is coupled with a low temperature metal hydride (LTMH) bed. In the present study, Mg-LaNi 5 composite hydrides are taken as HTMHs due to their high absorption capacity and high reaction enthalpy, and LaNi 5 based alloys are taken as LTMHs as these hydrides are ideal for hydrogen storage at ambient conditions. The thermodynamic properties such as reaction enthalpy and entropy are evaluated by measuring Pressure Concentration Isotherms of Mg- x wt% LaNi 5 ( x =20 and 30) composites, LaNi 4.7 Al 0.3 and LaNi 4.6 Al 0.4 . A new methodology for storing and recovering thermal energy together with upgradation of the quality of energy is established. Methodology to determine the minimum energy storage temperature and maximum energy recovery temperature is proposed. The quality of the thermal energy will be improved by increase in delivery temperature. Thermodynamic analysis is performed using measured properties to evaluate the performance parameters such as heat upgradation, coefficient of performance (COP), and energy storage density (ESD). Maximum COP and ESD of 0.705 and 418.841 kJ/kg, respectively is obtained for hydride pair Mg-5wt% LaNi 5 -La 0.8 Ce 0.2 Ni 5 . Maximum degree of upgradation of 34°C is obtained using the hydride pair Mg-20wt% LaNi 5 -LaNi 4.7 Al 0.3 . The effects of variation of heat source temperature, regeneration temperature and ambient temperature on the performance of the MHTES is studied. It is observed that the regeneration temperature is a significant parameter that influences the performance of the MHTES.

Performance optimization of electric vehicle battery thermal management based on the transcritical CO2 system

Thermal management of electric vehicles, especially battery thermal management, is critical to driving range and operational safety. To find a vehicle thermal management system with higher energy efficiency and environmental protection, an environmentally-friendly and efficient battery and cabin parallel cooling thermal management system was evaluated with CO2 as the working fluid. First, different control strategies of the evaporation temperature were compared regarding the battery cooling performance. Then, the effect of the battery cooling evaporation temperature on the coefficient of performance (COP) was explored. It was found that the maximum COP increased by 8.38% as the evaporation temperature decreased from 17 to 5.8 °C. Besides, it was found that the optimal battery cooling evaporation temperature range is 10.2–11 °C when the battery heating power is 0.4 kW. The vapor quality at the cold plate outlet should be lower than 0.95. Finally, the battery cooling performance under variable operating conditions was investigated. The influence of operating parameters on the battery cooling evaporation temperature and CO2 outlet vapor quality was also analyzed. Simulation results showed that the optimum evaporation temperature range varied significantly under different working conditions. The vapor quality at the cold plate outlet decreased slightly with the evaporation temperature.

Performance assessment of a perovskite solar cell-driven thermionic refrigerator hybrid system

To develop a high-performance solar refrigeration technology, a novel refrigeration system composed of a perovskite solar cell (PSC) and a thermionic refrigerator (TIR) is constructed. Based on theories of photovoltaic effect, thermionic emission and non-equilibrium thermodynamics, the coefficient of performance (COP) and refrigerating capacity of the integrated system are mathematically expressed, in which the various irreversible losses are taken into consideration. The integration characteristics and coupling relationships between the PSC and TIR are investigated, and the working voltage regions for the combined operation of the subsystems are determined. Furthermore, the impacts of the area ratio, the work function, the environment temperature, the cold reservoir temperature and the heat transfer coefficient on systemic performance are evaluated in detail. Numerical calculation examples illustrate that the maximum COP and maximum refrigerating capacity of the integrated system are 0.81 and 81.2 W, respectively. Analysis results show that there exist optimal area ratio and work function to optimize the system performance. The present study may offer some fresh perspectives on the evolution of the solar refrigeration system.

Active Air-Source Heat Storage and Release System for Solar Greenhouses: Design and Performance

The temperature difference between day and night in a solar greenhouse is large. Heat in a greenhouse is typically in excess during the day while the temperature is low and the humidity is high at night. This study designs and tests an active heat storage and release air-source heat-pump system with a thermally insulated water tank as the energy storage body. By comparing air temperature and humidity in a test greenhouse with a control greenhouse in typical weather conditions, the power consumption and performance of the system are evaluated. The results show that compared with the control greenhouse, the average daytime temperature of the test greenhouse is lowered by about 3 °C during the operation of the system in typical weather conditions. At night, the average temperature is increased by about 4 °C, and the relative humidity is decreased by about 20%. When optimized, the maximum coefficient of performance (COP) of the system can reach 4.32 in heat storage mode. The nighttime heat release from the energy storage tank accounts for 26.9% to 51.2% of the nighttime energy consumption, and the energy utilization efficiency is 59.6% to 497.0%. This study provides a new way to control environmental parameters in solar greenhouses.

Experimental Analysis for the Performance of a Geothermal Heat Exchanger Made of Environmentally Friendly Materials

Geothermal heat exchanger (GHE) technology is commonly used in residential and small non-residential buildings, and examples of innovative compact GHE designs are provided. The essential physical properties and processes involved in shallow GHE behavior are described, some of which may be more complex than those required for other types of GHE. This paper discusses the use of a geothermal heat exchanger to extract underground energy for heating and cooling systems and focuses specifically on designing a ground heat exchanger made of environmentally friendly materials suitable for working in the zone of Babylon Governorate in Iraq. At different burial depths, three systems of horizontal heat exchangers were designed. The heat exchanger was designed with pipes made of peroxide cross-linked polyethylene (PEX), in which the pipes were buried to a depth of 2 m under the soil. Also, another system was designed where the pipes are made of multi-layer composite pipe (Mlcp) at a burial depth of 2.5 m and another layer at a depth of 3 m. In this research, several tests were carried out to reach the conditions in which the ground heat exchanger is at its best performance. The effect of buried depth on heat removed from the space has been studied. This test was studying at a flow rate equal to (4 lpm) and the inlet temperature of water equal to approximately (50℃). The effect of changing the flow rates on heat removed from the ground heat transfer system is being studied. Buried depth of PEX pipes is 2m, inlet water temperature (50℃) is chosen as a case study to analyze this effect. The first experimental has shown the heat removed is equal to 2200.942 watts at 8.30 am when buried at a depth of 2m, while it reaches 3679.474 watts at a depth of 3 m. The results show the maximum coefficient of performance (COP) at (3 lpm) is 12.897 and it becomes 5.99 at 4 LPM. Also, the results show that the COP of PEX pipes can be higher than that of its counterparts when pipes are made from MLCp.

Investigation of the integrated fuel cell, battery, and heat pump energy systems

The integration of an advanced fuel cell battery electric vehicle was proposed to extend the driving range, increase the overall energy efficiency, and produce an additional cabin space heating service for on-board vehicle application in winter. The adopted heat pump absorbs heat from the fuel cell and battery during charging and discharging scenarios at the heat pump's cold end and transfers it to the cabin supply air for cabin heating. A numerical model for the proposed system was developed and validated by published experimental results. A comprehensive evaluation of the influence of fuel cell output current, battery discharging rate, ambient air temperature, evaporator coolant inlet temperature and refrigerant subcooling degree on the Coefficient of Performance (COP), outlet air temperature, and Equivalent Effective Battery Capacity (EEBC) were conducted. In addition, in this study, a detailed comparison of proposed system to previously published existing systems was carried out in terms of COP, heating capacity, EEBC, and operating price in order to examine the advantages of the proposed system. Results showed that the proposed system was not sensitive to ambient air temperature, but evaporator coolant inlet temperature had the greatest impact on COP, compared to other defined independent variables. A maximum COP of 6.07 could be observed when the evaporator coolant inlet temperature was 32 °C. Although increasing fuel cell output current and battery discharging rate could increase heating capacity, it would decrease outlet air temperature as well. The price of a single charging cycle for running for a 4-hour period was estimated. Compared to conventional Electric Vehicle Air Source Heat Pump (EVASHP) system and Positive Temperature Coefficient (PTC) heaters, the proposed system has the lowest cost which was £10.40per charging cycle while the others are £13.8 and £19.2 respectively when providing the same EEBC and heating capacity. Additionally, the payback period was 10,500 charging cycles. Overall, this study provides a potential solution for efficient cabin heating of electric vehicles in extremely cold weather with twice the EEBC of the existing EVASHP system and with 2.8 times of a PTC system both at −20 °C and the operating price is also 1/3 lower than the existing EVASHP. Meanwhile, the COP of the proposed system is 2.3 times that of the existing systems. It can sufficiently increase the driving range of electrical vehicles in winter and eliminate driving range anxiety.

Simulation and Experimental Study of CO2 Transcritical Heat Pump System with Thermoelectric Subcooling

In order to improve the efficiency of the system and promote its application in other industries, the performance of a thermoelectric subcooled CO2 transcritical heat pump system was studied. A simulation model of the system was established using steady-state lumped parameter technology, and the experimental data were compared with the simulation results. The effects of cooling and chilled water flow rate and temperature, subcooling degree, compressor discharge pressure on the coefficient of performance (COP), and heating coefficient of performance (COPh) were analyzed. The results showed that COP/COPh increased with the increase in cooling and chilled water flow rate and chilled water temperature and decreased with the increase in cooling water temperature. The experimental COPh and COP of the system with a thermoelectric subcooler increased by 4.19% and 4.62%, respectively, compared to the system without it. The simulated data was in good agreement with the experimental data, and the error was within 10%, thus verifying the correctness of the model. When the subcooling degree increased to 11 °C, the system simulation results showed that COP/COPh increased by about 40% and 13.3%, respectively. The optimal high pressure was about 8.0 MPa, which corresponded to the maximum COP and COPh of the system of 3.25 and 4.25, respectively. The research results can provide a theoretical basis for future system optimization.

Numerical simulations and optimized design on the performance and thermal stress of a thermoelectric cooler

In this article, the geometric optimum design of a thermoelectric cooler (TEC) is simulated by Finite Element Analysis. We studied the influence of the geometric structure on TEC parameters including the thermoelectric leg size, the separation distance of P/N legs, the distance from leg edge to copper edge and the copper thickness on the maximum temperature difference, the coefficient of performance (COP) and thermal stress. After optimizing designing, the TEC presented superior cooling performance and high operational reliability. The result demonstrates that the leg height plays the most important role in maximum temperature difference (ΔTmax) and thermal stress. At different thermoelectric leg width, by optimizing leg height, the ΔTmax can enhance about 9.079 K and the maximum thermal stress can reduce about 72.4 MPa. When the leg height is greater than 0.8 mm, its influence on temperature difference and thermal stress decreases. The separation distance of P/N legs play the most important role in the COP. By optimizing separation distance of P/N legs, the maximum temperature difference and COP all obtain the maximum value of 61.407 K, 0.663.

Numerical Study on the performance of a heat pump-driven-DCMD for sustainable desalination

The study presents an energy-efficient desalination system that combines direct contact membrane distillation (DCMD) and a heat pump to improve thermal efficiency and integrate with photovoltaics. DCMD is a sort of thermal desalination process, and it requires a lot of thermal energy. A heat pump is a device that produces both hot and cold energy simultaneously with less electrical energy input compared to other heating devices, such as a boiler and an electrical heater. A hollow-fiber DCMD and a 10-kW water-to-water heat pump were considered for a numerical simulation in this study. Numerical models were established for each device and validated against the results obtained from the literature. The simulation was first carried out to identify the performance of the system based on the baseline. After that, a series of simulations were carried out in order to investigate the performance of the proposed system in terms of specific energy consumption (SEC), gained output ratio (GOR), and the coefficient of performance (COP) under various operating conditions. Results showed that the minimum SEC and the maximum GOR were achieved at the inlet feed water temperature of 66.5°C with a mass flow rate of 20 kg/min and the inlet permeate temperature of 19.8°C with a mass flow rate of 10 lpm. On the other hand, it was found that the maximum COP can be observed at the inlet feed water temperature of 23.6°C with a mass flow rate of 10 lpm and at the inlet permeate temperature of 8.9°C with a mass flow rate of 20 lpm.

Influence of refrigerant charge and condenser area on direct-expansion solar-assisted heat pump system for radiant floor heating

As known, the refrigerant charge and condenser area have important influence on the thermal performance of a heat pump system. A test rig of a direct-expansion solar-assisted heat pump (DX-SAHP) system for radiant floor heating has been built, and the quasi-dynamic mathematical model of the system has also been established, which uses propane (R290) as the refrigerant. The deviations between the simulated results and experimental data are within 7.1 %, showing a good agreement. The analysis reveals that, when the refrigerant charge of the DX-SAHP system increases, the condensing pressure and the subcooling degree in the condenser increase, while the evaporating pressure decreases, resulting in the increase of the effect heat gain and the compressor power. The system coefficient of performance (COP) first increases to a maximum and then decreases with the refrigerant charge, and remains at a relative high level within a certain range near the optimal refrigerant charge. The optimal refrigerant charge is independent of solar insolation and ambient temperature, and decreases with initial water temperature in the hot water storage tank, while the corresponding subcooling degree is always in the 6–9 °C range. Furthermore, the system COP is also influenced by the condenser area. Both the maximum COP and corresponding optimal refrigerant charge are found to increase with the condenser area. As the condenser area increases from 0.553 to 1.393 m2, these two parameters increase by 8.95 % and 27.91 %, respectively.

Experimental performance of a vapor-injection CO2 heat pump system for electric vehicles in −30 °C to 50 °C range

Efficient and wide-range heat pump system is essential to improve the driving range and comfort of electric vehicles. In this paper, a vapor-injection transcritical CO2 heat pump system with a flash tank for electric vehicles was built up, and the heating and cooling performance in a wide range from −30 °C to 50 °C were experimentally studied. The maximum coefficient of performance (COP) at −30 °C/ 20 °C was 1.45, and the maximum COP at 50 °C/ 27 °C was 1.08. By comparing with the basic system without injection, it was found that the heating performance of the vapor-injection system was significantly improved, and the lower the outdoor temperature, the greater the improvement. The COP and heating capacity of the vapor-injection system were increased by 45.5 % and 75.7 % respectively at −30 °C/ 20 °C. Under the cooling conditions, only when the outdoor temperature was lower than 40 °C, the vapor-injection system had an advantage, and the maximum increments of COP and cooling capacity at 35 °C/ 27 °C were 9.5 % and 16.8 %, respectively. Further, a relationship model between vapor injection and compressor structure and operating conditions was established according to the working principle of the twin rotary compressor. The experimental verification showed that the deviation was within 8 %, which could provide a basis for the construction of the CO2 vapor injection heat pump system model.

Performance optimization of diffusive mass transfer law irreversible isothermal chemical pump

Performance optimization of generalized irreversible isothermal chemical pump (GICP) cycle with two-mass-reservoirs is performed. Three types of losses, that is, irreversible mass-transfer (IMT) between reservoir and working medium, internal dissipation (ID) inside working medium, and mass-leakage (ML) between reservoirs are included in GICP cycle. Diffusive mass transfer law (MTL) is assumed in IMT and ML processes. Performance relationship between rate of energy pumping (REP) and coefficient of performance (COP) is obtained using numerical examples, and it includes special examples with different loss items, which are derived analytically. The COP versus REP characteristic behaves a parabolic-like cure, that is, COP has maxima at an optimal REP. The COP and REP of GICP with diffusive MTL are compared with those with linear MTL. The effects of chemical potential ratio of mass-reservoirs, IMT, ML and ID on the COP versus REP characteristics are also shown. Maximum COP and the corresponding REP with diffusive MTL are smaller than those with linear one. COP increases monotonically as REP decreases when ML can be ignored. If ML is considered, COP versus REP characteristic behaves parabolic-like one whether ID is ignored or not. Optimal performances are affected by ML qualitatively and by ID quantitatively.