Heating Coefficient Of Performance Research Articles

A novel hybrid-energy heat pump with refrigerant injection: Performance characterization and injection optimization

Heat pumps have been widely used for space heating towards sustainable buildings. Thermally-driven absorption heat pumps can greatly reduce electricity consumption but suffer from low reliability, low applicability or low efficiency under some circumstances. To address these problems, this study proposes a novel hybrid-energy heat pump (HEHP) with refrigerant injection, offering a high flexibility to gradually transform from an absorption cycle to a compression cycle. The refrigerant injection can reduce the required driving temperatures of the absorption sub-cycle, aiming to utilize energy with lower temperatures. Thermodynamic models have been established with verified accuracy to characterize the heating capacity, COP (coefficient of performance) and PEE (primary energy efficiency) under various refrigerant injection ratios (RAHP) and injection pressure ratios (CR). Results show that the constant-frequency HEHP yields more stable heating capacities while the variable-frequency HEHP yields more stable COPs. The COP increases significantly with RAHP, reaching 17.19~42.34 with a RAHP of 0.8 for the two HEHPs. As the CR increases, the heating capacity increases and the COP decreases, while the PEE decreases under better conditions (high Tgin and Tein). After injection optimization, the optimal CR is found to increase significantly as Tgin or Tein decreases, with maximum CR of 1.4~2.5. The maximum PEEs are 0.99~1.62, 1.02~1.52, 1.04~1.48, and 1.045~1.46 for RAHP of 0.2, 0.4, 0.6, and 0.8, respectively. The turning Tein from which a higher RAHP yields higher maximum PEEs rises from −10 °C to 8 °C as Tgin increases from 100 °C to 130 °C.

Performance assessment of ground-source heat pumps (GSHPs) in the Southwestern and Northwestern China: In situ measurement

Ground-source heat pump (GSHP) systems contribute significantly to the reduction in energy consumption and CO2 emissions. The vast territory, abundant geothermal sources, and different climatic zones of Southwestern and Northwestern China provide significant opportunities for the application of GSHP technologies. In this study, a statistical study was performed to assess the general performances and identify the existing problems of GSHP systems located in the abovementioned areas. Twenty-eight GSHP projects, including groundwater heat pumps, soil-source heat pumps, and surface water heat pumps were selected. Water temperature, energy consumption, coefficient of performance (COP), energy efficiency ratio (EER), and thermodynamic perfectibility were analysed. The energy efficiency of GSHP systems were assessed according to the national standard. In addition, barriers and problems in GSHP applications are discussed herein. It is concluded that the average cooling COPs of SSHP, GWHP and SWHP units are 4.9, 4.7, and 4.2, respectively, with SSHP unit being the highest. The average heating COPs of SSHP, GWHP and SWHP units are 4.3, 4.2, and 4.2, respectively with SSHP unit being the highest. The SSHP has the best performance in both seasons amongst three GSHP types. Furthermore, though 89% of the systems can meet the requirements of national standard, more than 50% of them work at the lowest allowable energy efficiency value. This paper attempts to provide essential clues for the adoption feasibility and technical guidelines of GSHPs in the target areas.

Experimental study on the performance of air source heat pump system with multiple parallel outdoor units

This paper presents a novel air source heat pump for heating of buildings named air source heat pump with multiple parallel outdoor units (ASHPMO). Multiple outdoor units were connected in parallel with the aim of realising alternate defrosting and uninterrupted heating simultaneously. An experimental apparatus of the ASHPMO system was developed. The defrosting performance was experimentally investigated under different outdoor air temperatures, outdoor air relative humidity, and condensation temperatures, among other factors. The test results showed that the novel ASHPMO system could provide continuous heating when defrosting even under an outdoor air temperature of −10°C. Variations in compressor vapour suction and discharge pressure and temperature were observed. The minimum heating capacity could still reach 60% of that without defrosting. Under the defrosting condition with outdoor air temperature −10°C, both the heating coefficient of performance (heating COP) and total energy efficiency ratio (EER) of the system can reach to 2.0 and 2.32, respectively.

Performance analysis of solar assisted heat pump coupled with build-in PCM heat storage based on PV/T panel

PV/T (photovoltaic/thermal) technology is a combination of PV module (photovoltaic utilization) and collector (photothermal utilization), which can improve the comprehensive utilization efficiency of solar energy and has a broad application prospect. In this paper, PV/T module is coupled with heat pump evaporator to form a direct-expansion solar PV/T heat pump which is suitable for heat application in high latitude area. To achieve stable residential heating, a solar PV/T heat pump system coupled with build-in PCM (phase change material) heat storage is therefore proposed and simulated. Meanwhile, the mathematical model of solar PV/T heat pump coupled with build-in PCM heat storage system is established and verified. The simulation results show that the temperature of underfloor heating which using build-in PCM heat storage can reach 22–31 °C after 39 h when the circulating water is 40 °C. Moreover, the heating COP (Coefficient of Performance) increases with the increase of solar radiation, ambient temperature and area of PV/T collector, and decrease of wind speed, respectively. A 20 m2 PV/T panel module can output 21.4% of the electricity to power grid when the solar radiation intensity is 600 W/m2 and meet the heat demand of a 100 m2 room while maintain the operation of the system. Meanwhile, the heating COP can reach 5.79 which is 70% higher than the conventional air conditioning system and the electrical, thermal, overall efficiencies are 17.77%, 55.76% and 75.49%, respectively.

Field tests on thermal response characteristics of micro-steel-pipe pile under multiple temperature cycles

Energy piles have dual function of supporting a superstructure and acting as a shallow geothermal heat exchanger. Field tests on the thermal response characteristics of micro-steel-pipe piles under five operating temperature conditions (summer intermittent: 12 h for heating and 12 h for stopping as a cycle, winter intermittent: 12 h for cooling and 12 h for stopping as a cycle, summer continuous, recovery and winter continuous) were conducted. The heat transfer efficiency, the coefficient of performance (COP), the temperature and thermal induced stress of micro-steel-pipe piles were measured and analyzed. The results indicated that values of the heat transfer efficiency and COP were decreased with the process of cycles. The average COP and the average heat exchange rate per unit length under summer intermittent condition were relative higher than those in the corresponding period under summer continuous condition (the same trend in winter). The heat transfer efficiency in winter conditions was relative lower than that in summer conditions. In this field test condition, the additional compressive stress in micro-steel-pipe piles was increased by 200 kPa/°C, and the average heat exchange rate per metre was −49 W/m under Condition 5, 95 W/m under Condition 3.

Study on the Performance of Organic Rankine Cycle-Heat Pump (ORC-HP) Combined System Powered by Diesel Engine Exhaust

This study presents an ORC-HP combined system driven by diesel engine exhaust. This paper focuses on the feasibility and performance of the combined system under heating mode to heat a coach. The performances of the combined system with different parameters, including condensation temperature and evaporation pressure in ORC system, gas cooler outlet pressure, gas cooler outlet temperature and evaporation temperature in HP system, have been analyzed. The results show that the combined system can fully meet the demand of heat production. The optimal flow division ratio (rp) of 0.32 is selected by analyzing the system performance. Low condensation temperature is beneficial to the combined system performance. There exists a suitable range of evaporation temperature, gas cooler outlet pressure and gas cooler outlet temperature to achieve excellent performance. The heating coefficient of performance (COPh) shows a first increasing and then decreasing trend with gas cooler outlet pressure, namely there exists an optimal gas cooler outlet pressure that achieves the maximum COPh. The maximum total efficiency, COPh and heating capacity can reach up to 48.44%, 4.78 and 176.56 kW, respectively. These results show significant energy savings by applying the ORC-HP combined system.

Experimental study of heat and mass recovery on steam generation in an adsorption heat pump with composite zeolite-CaCl2

High-temperature steam generation in adsorption heat pump with composite zeolite-CaCl2 has been experimentally investigated by introducing heat and mass recovery. A direct contact heat exchange method is utilized to enhance the overall heat transfer rate. Composite zeolite (CZ) is prepared by immersing zeolite particle in CaCl2 solution at mass concentration of 40%. Cyclic experiment consists of two processes: regeneration with 130 °C dry air and steam generation with 80 °C hot water. The heat and mass recovery with steam below 90 °C is added before generation process. Mass of generated steam above 200 °C is increased by 9.12%. The effective time for steam generation is dramatically extended by 18.33%. Adsorption and thermal equilibriums inside the packed bed are achieved more quickly with heat and mass recovery. Gross temperature lift for one-stage adsorption heat pump is above 100 °C. Coefficient of performance for heating (COPh) and specific heat power (SHP) are elevated by 9.55% and 9.23%, respectively. The increase in mass of generated steam contributes to the improvement of COPh. Meanwhile, only a short time used for heat and mass recovery enables the rise in SHP.

Experimental study on CO2/R32 blends in a water-to-water heat pump system

The purpose of this study is to evaluate the cooling and heating performance as well as the compressor operating conditions of CO2/R32 blends in a water-to-water heat pump system. Experiments were conducted to reveal the effects of the refrigerant compositions, heat source temperatures, and internal heat exchanger (IHX) on the performance of the system. The results show that 23.3% and 65.2% maximum improvement in heating coefficient of performance (COPh) and cooling coefficient of performance (COPc) of the system were obtained when the mass fraction of CO2 was 0.6, respectively. Meanwhile, heating capacity, cooling capacity, and the compressor discharge pressure of CO2/R32 blends were decreased significantly. The thermal matching between the heat source and CO2/R32 blends significantly affected the overall performance of the system. In addition, IHX is recommended in the water-to-water heat pump to improve the system performance.

Performance analysis of high-temperature water source cascade heat pump using BY3B/BY6 as refrigerants

In this study, a high-temperature water source cascade heat pump (HTWSCHP) system was developed, which could provide heat at a temperature of approximately 170 °C. In order to select the optimum refrigerant, six pairs of refrigerants were compared theoretically when the heating temperature varied from 100 °C to 170 °C and the evaporation temperature was 55 °C. An experimental setup was used to compare the performance of BY3A/R245fa, BY3B/R245fa and BY3B/BY6 in the HTWSCHP with heating temperature in the range 100–140 °C. The theoretical results led to the selection of BY3B/BY6 as the best refrigerants for HTWSCHP, and the experimental results also showed better performance of BY3B/BY6. Moreover, this system using BY3B/BY6 produced hot water with the highest temperature of 168.4 °C. The coefficient of performance (COP) of the system was the best when the temperature lift was 70 °C compared to other heat pump systems, and the maximum temperature lift reached 113.4 °C. The experimental values of heating capacity, input power, COP, and discharge pressure were in good agreement with the theoretically calculated values. In addition, the results showed that the application scope of the HTWSCHP using BY3B/BY6 as refrigerant should be lower than 155 °C, for the safety of equipment and the economic challenges of practical application.

Theoretical Analysis of the Cooling Performance of a Thermoelectric Element with Temperature-Dependent Material Properties

Thermoelectric (TE) cooling may play a significant role in the electronic industry in the near future due to advantages such as static cooling and environmentally friendly properties. However, temperature-dependent material properties make theoretical analysis of the cooling performance challenging. In this work, a theoretical model is proposed to predict the performance of a thermoelectric cooler considering the temperature-dependent thermal conductivity, Seebeck coefficient, and electric resistivity. The governing thermal equation of the TE element is given, in which the thermal conductivity and Seebeck coefficient are nonlinear functions of temperature T, while the electric resistivity adopts the value reached at mean temperature. The performance of the TE cooling element, such as temperature field, cooling power, and coefficient of performance (COP), etc., predicted by the proposed model agree well with the numerical and finite element result, which prove the validity of our theoretical model. The results suggest that the temperature-dependent thermal conductivity and Seebeck coefficient have the most notable influence on the heat flow and COP of the TE cooling element.

Performance comparisons of NH3/ionic liquid absorption–compression heat pump for increasing the utilization of geothermal energy

Geothermal energy is becoming increasingly attractive to mitigate global energy and environment crisis. Various hybrid heat pump systems were introduced for increasing the utilization of geothermal energy, and then the absorption–compression heat pump (ACHP) using novel NH3/IL (ionic liquid) mixtures was analyzed. The property model of NH3/IL mixtures and the thermodynamic model of the ACHP cycle were established. Parameter studies showed that there was an optimal pressure ratio to achieve the highest coefficient of performance (COP). The optimal pressure ratio increased and the highest COP decreased as the allowed absorption pressure decreased. In addition, a higher pressure ratio was needed to produce a larger temperature lift. A higher absorber temperature (heat sink) led to a lower COP, while a higher generation temperature (heat source) was beneficial to a higher absorber temperature. Among the investigated ILs, [OMIM][BF4] (1-octyl-3-methylimidazolium tetrafluoroborate) yielded the highest heating COP with the lowest pressure ratio.

Energy and exergy analysis of an air-source heat pump water heater system using CO2/R170 mixture as an azeotropy refrigerant for sustainable development

In this paper, the azeotropic mixture of CO2/R170 (0.78/0.22, mass fraction) is presented as a refrigerant to replace R134a in an ASHPWH system. On the basis of the first and second laws of thermodynamics, system performance and the exergy efficiency analysis are carried out for the system using both refrigerants. The results show that both the COPheat (coefficient of heating performance) and exergy efficiency of the system using the CO2/R170 mixture refrigerant are higher than that using the R134a, and the values can be increased by 31.3% and 30.6%, respectively. Moreover, the compressor discharge temperature for CO2/R170 is about 34.3–49.8 °C lower and the compression ratio of compressor also has a significant reduction (from 12.0417 to 3.2734), which leads to a higher lifetime for the compressors. So, the CO2/R170 mixture may be a good choice to substitute for R134a in ASHPWH systems. Also, a CO2/R170 ASHPWH system may be more suitable in cold region.

Simulation of heat pumps for simultaneous heating and cooling using CO2

This article presents the numerical model of a heat pump using CO2 in a transcritical cycle. Two systems are envisaged in this work: a heat pump for simultaneous heating, cooling and domestic hot water (HPS1) and a heat pump for simultaneous cooling and desalination (using heat) (HPS2). The simulation study uses EES and TRNSYS to assess the performance of two heat pumps in different applications and operating conditions. The simulations show interesting performance indicators: the seasonal COP for heating and cooling and the exergy efficiency for both systems. HPS2 producing cooling and desalination has a higher seasonal process exergy efficiency than HPS1 due to the interesting use of energy for the desalination application. The performance analysis presents a seasonal Coefficient of Performance (COP) between 2 and 3.

Experimental study on R1234yf heat pump at low ambient temperature and comparison with other refrigerants

In this paper, an integrated vapor injection compression heat pump system using R1234yf, R32, R410A, R22, and R134a as working fluids was developed, and their heating performances under low ambient temperature were quantitatively evaluated. An experimental bench was built to test the system?s working performance. The condensing temperature, evaporating temperature, power input, and other variables were analyzed to evaluate the system?s heating capability and energy efficiency. Test results showed that the R1234yf system can run at the evaporating temperature of ?20 ?C, but its heating coefficient of performance was 5% lower than R134a. The R1234yf vapor injection system provided very significant performance improvements for heating performance compared with no vapor injection: the heating capacity and heating coefficient of performance can be improved by 14.3% and 11.7%, respectively.

Agreeableness and reactive social behavior

In this work, a thermodynamic model based on a small CO2 water-source heat pump water heater is proposed and discussed. The usefulness of the model lies in the possibility of selecting the best operating point for the system. Moreover, the optimal combination of capillary tube geometry and refrigerant charge can be predicted by the proposed model. In this regard, relevant experimental tests were conducted to validate the simulation results. The experiment data showed that the model had a relatively good accuracy based on the tested unit. Comparing with the simulation results, the length of capillary tube was found to be shortened by 8.77% and the optimal refrigerant charge was increased by about 5% under the specific conditions. In addition, experimental study showed that a refrigerant charge reduction of 3.7% (260 g) could lead to coefficient of heating performance (COPheat) reduction of about 3.1%, and 103.7% (280 g) charge could reduce COPheat by about 0.346%. The empirical formula method and rated operating method could be used to calculate the optimal refrigerant charge on small CO2 water-source heat pump water heater system with an error less than 5.55%.

Psychophysiological mechanisms features of events sequences predicting in schizophrenia depending on neuroleptics different types

In this work, a thermodynamic model based on a small CO2 water-source heat pump water heater is proposed and discussed. The usefulness of the model lies in the possibility of selecting the best operating point for the system. Moreover, the optimal combination of capillary tube geometry and refrigerant charge can be predicted by the proposed model. In this regard, relevant experimental tests were conducted to validate the simulation results. The experiment data showed that the model had a relatively good accuracy based on the tested unit. Comparing with the simulation results, the length of capillary tube was found to be shortened by 8.77% and the optimal refrigerant charge was increased by about 5% under the specific conditions. In addition, experimental study showed that a refrigerant charge reduction of 3.7% (260 g) could lead to coefficient of heating performance (COPheat) reduction of about 3.1%, and 103.7% (280 g) charge could reduce COPheat by about 0.346%. The empirical formula method and rated operating method could be used to calculate the optimal refrigerant charge on small CO2 water-source heat pump water heater system with an error less than 5.55%.

Performance analysis and optimization of new double effect lithium bromide–water absorption chiller with series and parallel flows

In this paper the effect of some key parameters on coefficient of performance (COP) in two novel arrangements of double effect lithium bromide–water absorption chillers with series and parallel flow have been studied. The main components of these cycles are generators, absorber, condensers, evaporator and heat exchangers. The mass, concentration, and energy balance equations are used for both cycles and performances of the systems are analyzed at different conditions with the condition of no formation of lithium bromide crystal. Also, the effects of temperatures and mass flow rates of inlet vapor of generator and inlet water of absorber on evaporator cooling capacity, absorber heat transfer rate and COP are investigated. In addition, two new parameters based on mass ratio of solution splitters are defined (R1 and R2) and their effects on the system performance are analyzed. The results show that the series cycle at inlet vapor temperature to the high temperature generator (HTG) below 150 °C has higher COP than the parallel cycle. In addition, with increase of inlet vapor temperature to HTG and rise of mass flow rate of inlet water to absorber, the COP increases in both parallel and series cycles. In addition, with increase of R1, the COP increases at first and reaches to a maximum value, and then decreases. Furthermore, the Genetic Algorithm (GA) method has been used to optimization of the system COP at series and parallel cycles.

Numerical Study of Integrated Solar Photovoltaic–Thermal Module with a Refrigeration System for Air-Conditioning and Hot Water Production under the Tropical Climate Conditions of Singapore

Thermal systems of buildings in the tropics are highly energy intensive. In this study, a novel integrated solar photovoltaic–thermal–refrigeration (PVTR) system used to produce hot water and air-conditioning in the tropical climate conditions of Singapore was analyzed. A dynamic simulation model was formulated for the analysis. Mathematical models were developed for the PV sandwich attached with a solar flat plate collector and for the main components of the refrigeration system. Thorough investigation of the electrical and thermal performances of the system were conducted through the analysis of coefficient of performance (COP), cooling capacity, water temperature and heat capacity in water heater, photovoltaic (PV) module temperature and PV efficiency. The results show that attractive electrical and thermal performance can be achieved with a maximum annual cooling COP of 9.8 and a heating COP of 11.3. The PV efficiency and power saving were 14% and 53%, respectively. The annual cooling, heating and PV energy produced were 9.7, 15.6 and 1.6[Formula: see text]MWh, respectively. The financial payback period of the system was 3.2 years and greenhouse gas (GHG) emission reduction annually was 12.6 tons of CO2 equivalents (tCO2e).

Application of response surface methodology in optimization of automotive air-conditioning performance operating with SiO2/PAG nanolubricant

The effect of compressor speed, initial refrigerant charge and volume concentrations of SiO2/PAG nanolubricant on the performance of automotive air-conditioning (AAC) system are investigated in this study. Response surface method (RSM) was used in designing the experimental work and is based on face composite design. The developed quadratic models from RSM were helpful to envisage the response parameters namely heat absorbs, compressor works, and coefficient of performance (COP) to identify the significant relations between the input factors and the responses. The results depicted that adding SiO2 nanoparticle into PAG lubricant will enhance the COP of AAC. Optimization of independent variables was performed using the desirability approach of the RSM with the goal of maximizing the heat absorb and COP, consequently, minimizing the compressor work. The results revealed that the optimal condition with a high desirability of 73.4% for the compressor speed of 900 rpm, refrigerant charge of 95 g and volume concentration of 0.07%. At this condition, the AAC system operated with 193.99, 23.28 kJ kg−1 and 8.27, respectively, for heat absorb, compressor work and COP. DoE based on RSM was capable of optimizing the significant parameters which affect AAC performance.

Optimal combination of capillary tube geometry and refrigerant charge on a small CO2 water-source heat pump water heater

In this work, a thermodynamic model based on a small CO2 water-source heat pump water heater is proposed and discussed. The usefulness of the model lies in the possibility of selecting the best operating point for the system. Moreover, the optimal combination of capillary tube geometry and refrigerant charge can be predicted by the proposed model. In this regard, relevant experimental tests were conducted to validate the simulation results. The experiment data showed that the model had a relatively good accuracy based on the tested unit. Comparing with the simulation results, the length of capillary tube was found to be shortened by 8.77% and the optimal refrigerant charge was increased by about 5% under the specific conditions. In addition, experimental study showed that a refrigerant charge reduction of 3.7% (260 g) could lead to coefficient of heating performance (COPheat) reduction of about 3.1%, and 103.7% (280 g) charge could reduce COPheat by about 0.346%. The empirical formula method and rated operating method could be used to calculate the optimal refrigerant charge on small CO2 water-source heat pump water heater system with an error less than 5.55%.