Experimental Investigation on a Vapor Injection Heat Pump System with a Single-Stage Compressor

Hongzhi Liu,Takao Katsura,Yue Han,Katsunori Nagano

doi:10.3390/en13123133

Hongzhi Liu, Takao Katsura + Show 2 more

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https://doi.org/10.3390/en13123133

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Abstract

In this study, a heat pump of 10 kW with vapor injection using refrigerant of R410A was developed. A vapor injection pipe connecting a gas–liquid separator at the outlet of the main expansion valve and the suction of a single-stage rotary compressor was designed. The heating performance of this vapor injection heat pump was investigated and analyzed at different compressor frequencies and primary temperatures. The experimental results show that for the heat pump without vapor injection, the heating capacity increased linearly with the compressor frequency, while the heating coefficient of performance (COP) decreased linearly with the compressor frequency for each tested primary temperature. The developed vapor injection technique is able to increase the heat pump system’s heating capacity and heating COP when the injection ratio R falls into the range 0.16–0.17. The refrigerant mass flow rate can be increased in the vapor injection heat pump cycle due to the decreased specific volume of the suction refrigerant. The power consumption of vapor injection heat pump cycle almost remains the same with that of the conventional heat pump cycle because of the increased refrigerant mass flow rate and the decreased compression ratio. Finally, it was found that the developed vapor injection cycle is preferable to decreasing the compressor’s discharge temperature.

Highlights

The energy consumed in the building sector is about 20% of the world’s delivered energy consumption, and it increased by 1.3% per year from 2018 to 2050 [1]
A vapor injection heat pump cycle by injecting vapor refrigerant separated by a gas–liquid separator into the suction port of a single-stage compressor has been developed
The performance of the developed single-stage vapor injection heat pump has been evaluated under different compressor frequencies and primary temperatures experimentally

Summary

Introduction

The energy consumed in the building sector is about 20% of the world’s delivered energy consumption, and it increased by 1.3% per year from 2018 to 2050 [1]. About half of the total building energy consumption is used for space heating and hot water supply [2]. Heat pumps are mechanical devices to transfer heat energy from a lower to higher temperature level mainly for space and hot water supply, which mainly includes a mechanical vapor compression cycle, an absorption cycle and an adsorption cycle [3]. The heat-operated absorption and adsorption cycles are suitable for application in a place where inexpensive heat source or waste heat is available because the compressor is not needed in these heat pump cycles Their achievable coefficient of performance (COPs) are lower than that of the mechanical vapor compression heat pump cycle, which is widely used nowadays [4]. Continuous efforts with regard to research on more efficient systems have mainly focused on viewpoints using alterative cycles [7,8,9,10] and the use of new refrigerants [7,11]

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