Heating Coefficient Of Performance Research Articles

Experimental study of a new multifunctional water source heat pump system

A new multifunctional water source heat pump system is presented in this paper. The new technical program, consisting of the refrigerant system and water system, can achieve a variety of functions in its yearly work process. In the heating mode, hot water is produced by two-step heating. An experimental research on the program is implemented through the establishment of experimental platform, and the results are presented as follows: under the function of cooling and heat recovery, (15.4–57)% of the total condense heat can be recovered, when the inlet water of heat source heat exchanger is at a certain temperature, the refrigerating capacity remains about the same with the decrease of water flow in the heat source heat exchanger. Under the function of individual cooling, an added water-to-water heat exchanger stabilizes the operation of refrigerant system in the new technical program, increases the cooling coefficient of performance (COPc) and at the same time reduces the scaling risk of heat source heat exchanger. When the new technical program is operated with the large temperature difference of hot water in the heating mode, the heating coefficient of performance (COPh) and the heating capacity are elevated, the power of compressor reduced.

Comparison of energy performance of heat pumps using a photovoltaic–thermal evaporator with circular and triangular tube configurations

In this work, the energy performance parameters of heat pumps using a photovoltaic–thermal evaporator (PV–TE) with circular and triangular tube evaporator configurations are compared. The experimental observations were made in a heat pump under the meteorological conditions of Coimbatore city in India. The standard energy performance parameters of a heat pump (using PV–TE) such as, condenser heating capacity, coefficient of performance (COP), evaporator heat gain, solar energy input ratio and photovoltaic panel efficiency were calculated using experimental observations. The energy performance parameters of the heat pump were simulated using artificial neural networks to have a realistic energy performance comparison. The results show that triangular tube PV–TE configuration has enhanced the major energy performance parameters of the heat pump such as, condenser heating capacity, COP and panel efficiency by 3%–7%, 3%–5% and 4%–13%, respectively when compared to the circular tube PV–TE configuration.

재열기를 사용한 고성능 VI 사이클 열펌프의 난방 성능 특성에 관한 연구

In this study, the characteristics of heating performance of a high-performance air-cooled heat pump with vapor-injection(VI) cycle using re-heater was investigated experimentally. Devices used in the experiment is consist of a VI compressor, condenser, oil separator, refrigerant (economizer outlet refrigerant) re-heater, economizer, evaporator. And R410A was used as a working fluid. The experiment was conducted with two cycles(cycles A and B) for investigating heating performance. In case of cycle B, heat exchange was conducted by re-heater between outlet refrigerant of compressor and suction refrigerant of the VI system(Fig.1, re-heater). But the re-heater was not used in case of cycle A. As a result of this experiment, discharge temperature of refrigerator in compressor was shown higher value, when the cycle B was conducted, because of the heat exchange between suction refrigerant of VI cycle and outlet refrigerant of compressor in the re-heater than cycle A that was not use re-heater. it means that liquid hammer and the decrement of heating performance can be decreased by using re-heater. Also, Heating coefficient of performance(COPh) was shown about 2.98 in Cycle B which was 4% higher than Cycle A and from these results, It was confirmed that the improvement of the heating performance of heat pump with VI cycle can be achieved by applying re-heater.

Field measurement and energy efficiency enhancement potential of a seawater source heat pump district heating system

As a renewable energy utilization system, seawater source heat pump district heating system can eliminate the local air pollution compared with the direct combustion of fuel in the conventional boiler house district heating system in northern cold climate area. A field measurement with an emphasis on the energy efficiency of an actual seawater source heat pump district heating system was conducted and analyzed. The field measurement showed that the heat pump units consumed the largest part of energy consumption of the whole system (as high as 78.9% in the project). However, the coefficient of heating performance (COP) of the seawater source heat pump unit was as low as 2.43. Then the energy efficiency enhancement potential of the heat pump unit was carefully analyzed and calculated in the light of the index of Thermodynamic Perfectibility for the heat pump unit. And the results showed that there is about an average of 24.2% energy efficiency enhancement potential of the heat pump units in the project. In the end, a verification case study indicated that the COP of the heat pump units in the project will increase 34.6% if they are substituted by the ones made by another manufacturer.

Research on the performance of the household-type cooling–heating–hot unit in winter

A smart air conditioning unit with functions of cooling, heating and hot water supply (referred to as CHU) is proposed for heating or cooling of residential buildings. The CHU can provide cooling and heating as regular heat pump air conditioning, and also produce hot water by recovering condensation heat in summer. To study the performance of this innovative system, a prototype machine of CHU is implemented consisting of compressor, water pump and data acquisition system. In this paper, the investigation of the proposed system is focused on the performance in winter mode. Firstly, the performance of CHU for generating hot water is tested in the air source heat pump mode. Furthermore, experiments are executed on the air source and water source heat pump modes, respectively, to test the operation performance in winter conditions. The experimental results show that the system's coefficient of heating performance (COP) decreases with the condenser inlet water temperature, which selected R22 as the refrigerant material. Besides that, both modes show significant energy saving and environmental benefits, with the COP in water source mode a little larger than in air source mode.

Case study of performance evaluation of ground source heat pump system based on ANN and ANFIS models

This paper presents case studies with a method to predict the coefficient of performance (COP) of the heat pump and the COPs of ground source heat pump (GSHP) system with limited parameters. The method was based on an artificial neural network (ANN) model and an adaptive neuro-fuzzy inference system (ANFIS) model. Two GSHP systems were monitored respectively to get the training and test data. ANN models with different neurons in the hidden layer were compared according to the statistical validation results, and the models with five neurons in the hidden layer appears to be the best optimal topology for the prediction of COP of the heat pump and COPs of the system. ANFIS with different membership functions (MFs) and various numbers of MFs were compared. Gaussmf with three functions appeared to be the most optimal membership function for the ANFIS model calculating the COP of the heat pump. The optimal ANFIS was the model with two Gaussmf as its member function to predict the COPs of the system. It was found that the models provided high accuracy and reliability for calculating performance indexes of GSHP system.

Cascaded energy plant using ammonia absorption refrigeration system for combined cooling and heating applications

A cascaded energy plant for the pharmaceutical industry has been developed and implemented to generate chilled water at 7°C and hot water at 58°C for the required applications using ammonia absorption refrigeration system making use of low-grade thermal energy, such as steam. The internal heat recovery (Qihr) of an ammonia–water absorption refrigeration system was improved with additional components. The additional components, such as a generator heat exchanger and solution cooled rectifier, significantly improved the system performance compared to the systems using only conventional components (evaporator, generator, condenser, absorber, solution heat exchanger, and economizer). In addition to the conventional components, the condensate cooler has been added to the system for condensate heat recovery. The system delivers the cooling and heating coefficients of performance of 0.6 and 1.53, respectively, for the tested conditions with a steam inlet temperature of 147°C, cooling process water inlet temperature of 30°C, and chilled water inlet temperature of 15°C. The developed system delivers 300–430 kW of cooling load and 700–1100 kW of heating load, depending on the cooling load of the plant requirement since installation.

Binary blend of carbon dioxide and fluoro ethane as working fluid in transcritical heat pump systems

As an eco-friendly working fluid, carbon dioxide or R744 is expected to substitute for the existing working fluids used in heat pump systems. It is, however, challenged by the much higher heat rejection pressure in transcritical cycle compared with the traditional subcritical cycle using freons. There exists a worldwide tendency to utilize blend refrigerants as alternatives. Therefore, a new binary blend R744/R161 in this research is proposed in order to decrease the heat rejection pressure. Meanwhile, on mixing R744 with R161, the flammability and explosivity of R161 can be suppressed because of the extinguishing effect of R744. A transcritical thermodynamic model is developed, and then the system performances of heat pump using R744/R161 blend are investigated and compared with those of pure R744 system under the same operation conditions. The variations of heat rejection pressure, heating coefficient of performance, unit volumetric heating capacity, discharge temperature of compressor and the mass fraction of R744/R161 are researched. The results show that R744/R161 mixture can reduce the heat rejection pressure of transcritical heat pump system.

Cycle performance of air conditioning system based on finned tube heat exchangers with different helix angles

The cycle performance of the novel 5 mm outer diameter (OD) finned tube heat exchangers (FTHX) with different helix angles (1°, 6°) were investigated as indoor unit in split air conditioning systems to be compared with those of the conventional indoor ones (5 mm and 7 mm FTHX with helix angle of 18°). Conventional T-splitter of the outdoor heat exchanger (HX) was afterward replaced by a Y-splitter and numbers of U-tubes in the two bypasses were adjusted to balance the heat exchange amount of two different bypasses. At first, experimental results showed that the 5 mm system with helix angle of 6° was superior to those 5 mm systems with helix angles of 1° and 18° but still inferior to the conventional 7 mm system, in aspects of capacity and coefficient of performance (COP) both in cooling and heating mode. But after the adjustments, performance of the 5 mm system with helix angle of 6° experienced a 1.5% and 0.7% higher capacity both in cooling and heating mode, respectively, and a 1.7% higher heating COP in spite of a 0.7% lower cooling COP. The system adopting the 5 mm tubes with the helix angle of 6° after adjustments is demonstrated that it can commendably ease material pressure and meanwhile promote the cycle performance.

Theoretical study of a thermoelectric-assisted vapor compression cycle for air-source heat pump applications

This paper proposes a thermoelectric-assisted vapor compression cycle (TVCC) for applications in air-source heat pump systems which could enhance the heating capacity of the system. Performances of TVCC are calculated and then compared with that of basic vapor compression cycle (BVCC). The simulation results show that when coefficients of performance (COPs) of the two cycles are almost equal, the TVCC under maximum COP condition of the thermoelectric modules still performs better than BVCC by 13.0% in heating capacity through selecting the appropriate intermediate temperature. In addition, the TVCC can also achieve an improvement of 16.4%–21.7% in both the heating COP and capacity when compared with the BVCC with an assistant electric heater that is provided with the equivalent power input of thermoelectric heat exchanger. Thus, the TVCC could be beneficial to the applications in small heat pumps if there is always need for auxiliary electric heat.

Regenerated air cycle potentials in heat pump applications

Air (reversed Brayton) cycle has been utilized in the area of refrigeration and cryogenics for several decades, but its potentials in heat pump applications were longtime underestimated. In this paper, a thermodynamic model for the regenerated air heat pump cycle with practical compressor, expander and regenerated heat exchanger was developed. Based on the model, the relations between the system performance and the operating parameters were analyzed. The optimal heating COP (coefficient of performance) and the corresponding pressure ratio were derived. Then, air heat pump cycles (regenerated cycle and basic cycle) and vapor-compression heat pump cycles (CO2 trans-critical cycle and R410A subcritical cycle) were numerically compared. The results indicated that the regenerated air heat pump cycle not only gets the heating capacity in line with the heating load under different operating conditions but also achieves higher COP over trans-critical CO2 heat pump cycle in applications of large temperature difference.

The thermal performance of seawater-source heat pump systems in areas of severe cold during winter

The research concerning ocean energy exploitation in North China is undoubtedly of significant importance to the development of the national ocean energy. The use of seawater heat pump (SWHP) systems is a better choice than air-source heat pump (ASHP) systems. The latter systems have a lower efficiency because of the formation of frost on the surface of its airside heat exchanger when the ambient air temperature is low. This paper reports research investigating the system efficiency of SWHP systems in areas of severe cold during winter. Experiments are conducted to compare the thermal performance of the beach well infiltration intake systems (BWIS) and the helical coil heat exchanger (HCHE) for SWHP systems in the Bohai Sea, Tianjin, North China. Heat transfer rate, COP (coefficient of performance) values, exergy efficiencies and exergy destruction rates of the SWHP systems with BWIS and HCHE are presented and compared with the ASHP systems. The study results indicate that the BWIS for SWHP systems has the highest thermal performance during the whole heating season in areas of severe cold during winter. That performance is observed because icing on the outer surfaces of the tubes of the HCHE and frost formation on the surface of the heat exchanger of the ASHP have great effects on the heat transfer performance. The Heating seasonal performance factor (HSPF) is used to express the performance of heat pump systems over the entire heating season. Economic analyses of the BWIS and HCHE are performed according to local economics to compare the application of the HCHE and BWIS, and the results indicate that the HCHE has a better economic value.

Simulation and validation of a hybrid-power gas engine heat pump

Hybrid-power gas engine heat pump (HPGHP) combines hybrid power technology with gas engine heat pump, which can keep the gas engine working in the economical zone. In this paper, a steady-state model of the HPGHP in heating condition has been established, the optimal torque curve control strategy is proposed to distribute power between the gas engine and battery pack. The main operating parameters of the HPGHP system are simulated on Matlab/Simulink and validated by experimental data, such as operating temperature, coefficient of performance (COP), fuel-consumed rate, etc. Heating capacity and COP of the heating pump system are validated under different ambient temperatures and water flow rates. The simulation and experiment results shows acceptable agreement, the maximum difference is respectively 8.9%, 5.9%, 9.5% and 8.2% for engine torque, motor torque, reclaimed heat and fuel-consumed rate. Based on the simulation results, HPGHP has the lowest fuel-consumed rate of 283 g (kWh)−1 at engine speed of 3000 rpm; the PER of HPGHP system is about 15.9% and 11.4% higher than the GHP under the same load in Mode C and D.

AN EXPERIMENTAL STUDY ON PERFORMANCE IMPROVEMENT FOR AN AIR SOURCE HEAT PUMP BY ALTERNATE DEFROSTING OF OUTDOOR HEAT EXCHANGER

For a space heating air source heat pump (ASHP) in the condition of low temperature and high humidity, frost on the surface of heat exchanger becomes the major cause decreasing heating surface area and thus the performance of heat pump. In this study, we showed a method of delaying the implantation of frost using alternate defrost control. First, we acquired the performance data for conventional periodic reversed-cycle defrosting with a 5RT heat pump. After the experiment, the heat pump was modified to verify the effects of newly introduced alternate defrosting and compared with the conventional periodic reverse cycled method. It was found that heating coefficient of performance (COP) of heat pump using newly proposed alternate defrost method was about 17% higher than conventional heat pump using periodic reverse cycled defrosting.

An important feature of air heat pump cycle: Heating capacity in line with heating load

In the conventional vapor-compression heat pumps, the heating capacity and the heating load usually vary in opposite directions, which results in a mismatch of the heating capacity and the heating load at off-design conditions. Air (reversed Brayton) cycle is a potential substitute for the conventional vapor-compression cycles. This paper proved that in theory the air heat pump cycle can make the heating capacity in line with the heating load at a stable level of heating COP (coefficient of performance). A thermodynamic model for the air heat pump cycle with practical compressor and expander was developed. The optimal heating COP and the corresponding pressure ratio were derived from the model. Then the cycle performance was analytically expressed under the optimal COP conditions. The heating capacity under different operating conditions was found in line with the heating load. Comparisons between the air heat pump cycle and two typical vapor-compression heat pump cycles were numerically done for further verification. It also turned out that the energy efficiency of air heat pump is comparable to the transcritical CO2 heat pump, particularly at large temperature difference.

Thermodynamic analysis of an absorption system using [bmim]Zn2Cl5/NH3 as the working pair

The thermodynamic performance of an absorption system using [bmim]Zn2Cl5/NH3 as working pair for cooling and heating applications was numerically analyzed. Changes in the coefficient of performance (COP) and exergetic efficiency for [bmim]Zn2Cl5/NH3 absorption refrigeration with varying generation temperature, absorption temperature and condensation temperature were simulated and compared with that of the NaSCN/NH3 system. It was observed that the COP and exergetic efficiency of the [bmim]Zn2Cl5/NH3 system are slightly higher than that of the NaSCN/NH3 system when the generation temperature is high and the condensing temperature and absorption temperature are low. The effects of the generation temperature on the COP and the circulation ratio for cooling were investigated and analyzed. The results indicate that the [bmim]Zn2Cl5/NH3 system is suitable for use in cooling applications. The effects of the generation temperature on the COP, exergy efficiency and circulation ratio for heating were evaluated and discussed. The findings indicate that the [bmim]Zn2Cl5/NH3 absorption system exhibits good thermal performance for heating applications.

Heating load and COP optimization of a double resonance energy selective electron (ESE) heat pump

A model of a double resonance energy selective electron (ESE) heat pump in one-dimensional system with two idealized energy filters is established in this paper. The analytical expressions of heating load and coefficient of performance (COP) for the ESE heat pump are derived. The optimum heating load and COP performances of the double resonance ESE heat pump are analyzed by using the theory of finite time thermodynamics. The effective regions of central energy level and heating load are obtained. The influences of energy space as well as resonance width of the two resonances on the performance of the ESE heat pump are discussed by detailed numerical examples. The values of some important performance parameters are also obtained by numerical calculations. The performance of the double resonance device is compared with that of the single resonance device. It is found that the maximum heating load decreases with the increase of energy space or the decrease of resonance width, while the maximum COP decreases with the increase of energy space or resonance width. By reasonable choices of the first resonance energy level, the energy space and the resonance width, the heat pump can be controlled to operate under the maximum COP condition. The results obtained herein can provide some theoretical guidelines for the design of practical multi-barrier nanostructured devices.

PERFORMANCE STUDY AND EXPERIMENTAL CYCLES OF TWO STAGE SOLAR HYBRID ADSORPTION REFRIGERATION SYSTEM

The performance parameters and experimental cycles of a solar adsorption refrigeration system working with the activated carbon-methanol working pair are presented here. Such a system has been fabricated and tested under the conditions of National Institute of Technology Calicut, Kerala, India. The performance parameters such as specific cooling power (SCP), coefficient of performance (COP), solar heating COP, solar cooling COP, uptake efficiency and exergy efficiency are studied. The dependency between the exergy efficiency and cycle COP with the driving heat source temperature for two thermal compressors is also studied. The optimum heat source temperature for the thermal compressor one is determined as 71.4oC and for the other thermal compressor it is 68.20C. The system has a mean cycle COP of 0.196 during day time and 0.335 for night time. The mean SCP values during day time and night time are 47.83 and 68.2, respectively. Experimental results also demonstrate that the adsorption refrigerator has cooling capacity of 47 to 78 W during day time and 57.6 W to 104.4W during night time. This study also presents the analysis of experimental thermodynamic cycle of solar adsorption refrigeration system. Two cycles have been analysed experimentally, one with clear sky and the other with partly cloudy. Use of artificial neural network model is proposed in order to predict the performance of the system. After training, it was found that LM algorithm with 9 neurons is most suitable for modeling solar adsorption refrigeration system. The ANN predictions of performance parameters are in good agreement with the experimental values with R2 values close to one and maximum percentage of error less than 5%. The RMS and covariance values are also found to be within the acceptable limits.

Experimental performance analysis of an improved multifunctional heat pump system

An improved multifunctional heat pump (MFHP) system that integrates an air-source evaporator and a water–water heat exchanger was developed. An experimental set-up and a mathematical model were constructed to evaluate the performance of the MFHP system. Some characteristics of the system, such as the effects of water–water heat exchanger, hot water outlet temperature, and cooling capacities of the air-source and water-source evaporators, were discussed based on experimental data. Experimental results show that the MFHP system could simultaneously supply hot water for bathing and cold air for air conditioning. In addition, the coefficient of heating performance (COPh) varied from 3.69 to 5.70. Analysis results show that the COPh and the hot water volumetric flow rate of the MFHP system were closely related to the inlet and outlet temperature of hot water and wastewater. Empirical models of COPh and hot-water flow rate were proposed to predict the heating performance of the MFHP system. The improved MFHP system is shown to have satisfactory energy saving performance.

Performance analysis of irreversible energy selective electron (ESE) heat pump with heat leakage

A model of an irreversible energy selective electron (ESE) heat pump with heat leakage is established in this paper. The general expressions for heating load and coefficient of performance (COP) of the ESE heat pump in the maximum heating load operation regime and the intermediate operation regime are derived respectively. The optimum performances of the ESE heat pump in these two different operation regimes are analysed by detailed numerical examples. The characteristic curves of COP versus heating load considering heat leakage in maximum heating load operation regime are parabolic-like ones, and the COP will approach a fixed value as the heating load increases. This is due to the fact that electrons that contribute positively to heat pumping are all transmitted through the energy filter in this regime. The characteristic curves of COP versus heating load with and without considering heat leakage in intermediated operation regime are all parabolic-like ones, and the COP will be below unity as the heating load increases, which results from the mixing of heat pump behaviour and heat engine behaviour of the electron system in this regime. The influence of the resonance widths on the heating load and COP performances of the ESE heat pump is discussed. Selecting the reasonable ranges of the central energy and resonance width, the ESE heat pump can be controlled to operate in the optimal COP condition. The results obtained herein can provide theoretical guidelines for analysing and improving the performance of micronanothermionic devices.