Simulation study on performance of a dual-source hybrid heat pump unit with alternative refrigerants

To solve the problems of single heat source heat pump systems in severe cold regions,a dual-source hybrid heat pump unit(DSHHPU)is proposed.The mathematical models of the DSHHPU when charging R134a or its alternative refrigerants R32,R290 and R600a were established respectively,and the performance was simulated and analysed.The results showed that the four refrigerants have different performance characteristics in different aspects.In heat pipe mode,the heating capacity and evaporating pressure of R32 are 36.94%and 59.94%higher than those of R134a.The heating capacity and evaporating pressure of R290 are 5.73%and 22.99%lower than those of R134a.The heating capacity and evaporating pressure of R600a are 43.29%and 68.08%lower than those of R134a.In vapour compression heating mode,the discharge temperature of R32,R290 and R600a are 184.88,72.98 and 66.44%of that of R134a.The coefficient of performance(COP)of R32,R290 and R600a are 72.65,111.59 and 117.94%of that of R134a.Finally,the effects of radiation intensity and ambient temperature on key performance parameters of the different refrigerants were analysed.The research results provide a reference for research on refrigerant replacements for multi-heat source composite heat pump systems.

Experimental Performance of TJR02 as an Alternative Refrigerant to R22 in a Small-Scale Cold Storage

A refrigerant mixture TJR02 was developed and the comparison experiment was performed on a singlestage vapor compression refrigeration system originally designed for R22.Experimental results show that TJR02 can be directly used in the system without modifying the original system or changing lubricant.By replacing R22 with TJR02,cooling rate gets faster and at least 20% of energy is saved.The actual detection in the standard test-bed verifies the experimental results and indicates that the adoption of TJR02 leads to greater efficiency and wider application.And the lower the refrigeratory temperature is,the more obvious the energy saving effects will be.

Critical assessment of R410A alternatives for mini-split air conditioners in the Egyptian market

In this study,the potential implementation of three different low-GWP refrigerants(R32,R452B,and R454B)as replacements for R410A was investigated.The study was performed using a simulation tool developed by the authors called RACHP-Lab,which is a vapor compression system simulation tool developed based on physics-based simulation for typical mini-split air conditioners.The simulation study was carried out and validated using experimental performance data of 10 different air conditioning units available in the Egyptian market.The units included fixed-speed or variable-speed compressors and operated in cooling or heating modes.Drop-in replace-ment with the new refrigerants was carried out.For R32,the capacity increased between 4.9%and 13%for cooling cases,and 6.3%and 12.4%for heating cases.However,COP did not improve in all cases.For R452B and R454B with direct replacement,the capacity nearly remained the same,with an increase of COP between 1.6%and 8.0%.Soft optimization was also conducted on cooling cases where compressor suction superheat,condenser subcooling,and compressor volumetric speed were optimized to maximize COP while maintaining the original capacity of R410A.R32 showed an improvement of COP over R410A between 4.6%and 15.5%,while for R452B and R454B between 2.2%and 13.2%.

Prospect Evaluation of Low-GWP Refrigerants R1233zd(E)and R1336mzz(Z)Used in Solar-Driven Ejector-Vapor Compression Hybrid Refrigeration System

In this paper,the entrainment ratio,pump work,heat loads of heat exchangers and COPthermal were theoretically evaluated for a solar-driven ejector-vapor compression hybrid refrigeration system with R1233zd(E)and R1336mzz(Z)as the working fluids.The evaluation of the utilization potentials of R1233zd(E)and R1336mzz(Z)was presented by comparing the system performance with that of R245fa,a commonly used refrigerant in the ejector system.The results indicated that the systems with R1233zd(E)and R1336mzz(Z)had a higher entrainment ratio and lower pump work.The pump works when using R1233zd(E)and R1336mzz(Z)can be up to 14.59%and 38.05%lower than those of R245fa,respectively.Meanwhile,the system showed the highest COPthermal utilizing R1233zd(E)followed by that of R245fa,with the R1336mzz(Z)system having the lowest value.The differences between R1233zd(E)and R1336mzz(Z)systems,R1233zd(E)and R245fa systems were 4.33%and 2.0%,respectively.This paper was expected to provide a good reference for the utilizing prospect of R1233zd(E)and R1336mzz(Z)in ejector refrigeration systems.

Cycle performance studies on a new HFC-161/125/143a mixture as an alternative refrigerant to R404

In this paper, a new ternary non-azeotropic mixture of HFC-161/125/143a （0.15/0.45/0.40 in mass fraction）, as a promising mixed refrigerant to R404A, is presented. The ozone depletion potential （ODP） of the new refrigerant is zero and its basic thermodynamic properties are similar to those of R404A, but its global warming potential （GWP） is much smaller than those of R507A and R404A. Meanwhile, theoretical calculations show that, under the working condition 1 （the average evaporation temperature： -23℃, the average condensing temperature： 43℃, the superheat temperature： 28℃, the subcooling temperature： 5 ℃）, the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.33% and 15.48% higher, re- spectively, than those of R404A. The coefficient of performance （COP） of the new mixture is 5.19% higher than that of R404A and the pressure ratio of the new mixture is 0.82% lower than that of R404A. Equally, under the working condition II （the average evaporation temperature： -40℃, the average condensing temperature： 35℃, the superheating temperature： 30 ~C, the subcooling temperature： 5℃）, the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.24% and 20.58% higher, respectively, than those of R404A. The COP of the new mixture is 4.60% higher than that of R404A and the pressure ratio of the new mixture is similar to that of R404A. The performances of the new mixture and R404A are compared in a vapor compressor refrigeration apparatus originally designed for R404A under several working conditions （condensing temperatures： 35-45℃, evaporation temperatures： -40--20℃）. Experimental results show that the new mixture can obtain a higher COP, by 6.3% to 12.1%, and a lower pressure ratio, by 1.8% to 6.6%, compared to R404A; although the discharge temperature of the new mixture is slightly higher than that of R404A. The advantages of the new mixture will be further verified in the actual system.

Thermophysical Properties of a New Environment FriendlyAlternative - Trifluoroiodomethane

Trifluoroiodomethane (CF3l) is consider as a Promising refrigerant alternative, especially as a component inmixtures, to replare CFC-12. But reliable thermophysical propelty data for CF3I are still limited. The investigationson thermophysical Propelties of CF3I developed by us are summarized in this paper. Experimental data of criticalParamethe, and the condations of saturated liquid and vapor density, enthaipy of vaporization, vapor pressurs,PVT prowtes, second vinal coefficient ideal-gas heat capacity, surface tension, viscosity and thermalconduchvity are given in the Present paper.

Influence of Tube's Diameter on Boiling Heat TransferPerformance in Small Diameter Tubes

This paper reports the experiments of evaporation study in 6 mm inner copper diamter tubes us-ing HFC-134a, HCFC-22 and CFC-12 as working nuid. The results show that the evaporation heat transfer coefficient increases with the decreasing of inner diameter of tubes. A new concept of non-dimensional tube diameter U is proposed in this paper for correction of the influence of the tube diameter on the evaporation heat transfer coefficient. And further, a convnient empirical correction mehod is pented.

PVTx Study of Binary System R22/R152a with Burnett Method

This paper reports the PVTx properties of R22/R152a system in the ranges of temperature from 298.15 K to 353.15 K and pressure from 0.288 MPa to 1.288 MPa. Sixty seven PVTx measurements for three compositions, i.e., 0.2712, 0.4094 and 0.7911 mole fraction of R22, have been measured along 16 isotherms. The uncertainties of temperature and pressure measurements are less than 0.01 K and ±500 Pa respectively. The reliability of the experimental measurements is confirmed by using REFPROP program, a computer program suggested by Morrison et al[4].