In this article, R1234ze(E), R152a, and three mixtures M1, M2, and M3 composed of R152a and R1234ze(E) (in the ratio of 60:40, 50:50, and 40:60, by mass, respectively) as drop-in replacements of R134a in vapor compression system were theoretically analyzed. The performance of the vapor compression system was compared in terms of compressor discharge temperature, volumetric cooling capacity, cooling capacity, compressor power consumption, and coefficient of performance. The results showed that R152a had better coefficient of performance as well as nearly equal volumetric cooling capacity and cooling capacity compared to R134a; however, flammable R152a running with high compressor discharge temperature was restricted. Cooling capacity of R1234ze(E) was far lower than that of R134a. M2 was selected as the best alternative for R134a. Volumetric cooling capacity of M2 and R134a was similar so that M2 can be used in R134a vapor compressor system without modifying compressor. Coefficient of performance of M2 was higher than that of R134a by about 3% with 7% lower cooling capacity and 10% lower compressor power consumption. Compressor discharge temperature of M2 was higher than that of R134a by about 2°C-5°C. It was concluded that M2 can primely be an energy conservation and environmental protection alternative to R134a in vapor compression system.
An instantaneous-heating air source heat pump water heater with a temperature stratified water tank was put forward. The instantaneous-heating air source heat pump water heater was designed to produce hot water instantly by three modes, namely condenser heating, water tank heating and condenser-water tank joint heating. The heating mode is chosen as condenser heating when the ambient temperature is above 20°C (including 20°C) and is chosen as condenserwater tank joint heating below 20°C. A 3HP instantaneous-heating air source heat pump water heater was built and tested in an Enthalpy Lab. Influences of refrigerant charge, throttle step, compressor frequency on heat capacity, and heat coefficient of performance were analyzed, and the effect of thermal stratification of the buffer tank and the operation performances in various conditions (according to China's National Standard GB-23137) were tested. The results showed that the instantaneous-heating air source heat pump water heater can generate 42°C and 6 L/min hot water at ambient temperatures of 20°C and 43°C with heat coefficients of performance (of the instantaneous-heating air-source heat pump water heater) of 4.5 and 12.7 respectively, and at ambient temperature 27°C with a heat coefficient of performance (of the heat pump module) of 2.76. It also showed that the advantage of the system is the compressor's suction and exhaust pressures in certain working conditions are steady and the effect of the temperature stratification of the buffer tank is significant. In conclusion, the instantaneous-heating air source heat pump water heater has great application value for household.
A readily available effective adsorbent is necessary to adsorb heavy-metal ions from aqueous solutions. In this study, a novel adsorbent with good adsorption properties [Al 3+ -oligomer-pillared diatomite (Al 3+ -oligomer-PD)] was prepared and was used to adsorb Cd 2+ ions in a solid/liquid system. The property and nature of the Cd 2+ ions adsorbed on the surface of the Al 3+ -oligomer-PD were studied by performing a series of adsorption tests and related surface property analyses. Our study results show that owing to a more favourable pore structure, the PD has a higher adsorption property compared with natural diatomite (ND) and most other common adsorbents. The adsorption capacity of PD is 27.36% greater than ND and also achieves an optimal value of 10.05 mg/l. Certain parameters have a significant effect on Cd 2+ ion adsorption. The most suitable isotherm and kinetics models for describing the adsorption of Cd 2+ ions are the Freundlich and pseudo-secondorder models. The nature of Cd 2+ ion adsorption on PD is favourable, physical, spontaneous, exothermic and disorder increasing. The results of the study suggest that PD is an ideal adsorbent for the removal of cadmium ions from aqueous solutions.
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