A multi-connected air-conditioning system having one outdoor unit and four indoor units, with 5 HP constant speed scroll compressor paralleled with 4 HP frequency inverter scroll compressor, was developed. Many experiments were taken under different working conditions and different system parameters. The performances and the operating characteristics were obtained. The oil-back ability was vali...

Conventional control of household refrigerators is typically accomplished with simple, single-sensor control systems. Though cost-effective this approach allows temperature dependencies to exist between compartments, producing non-optimal energy consumption. In order to study the performance of the conventional refrigerator a computer model was developed. Analytical results were generated to de...

Improving the cooling systems is one feasible technique to ameliorate the characteristics of compressor installations. This paper presents the results of theoretical and experimental researches of staged compressed gas cooling process through several coolants with arlferent properties in multisection gascoolers. The theoretical investigation was conducted using a developed mathematical modeL wh...

The heating capacity and coefficient of performance (COP) of conventional air-source heat pumps decreases towards lower ambient temperatures. Additionally, the heat pump stops running at very low ambient temperatures due to the high discharge temperature at the outlet of the compressor. Oil injected into the compression chamber absorbs the heat generated during the compression process and thus,...

Information technology (IT) has brought significant changes in people’s lives. As an important part of the IT industry, data centres (DCs) have been rapidly growing in both the number and size over the past 40 years. Around 30% to 40% of electricity consumption in DCs is used for space cooling, thus leading to very inefficient DC operation. To identify ways to reduce the energy consumption for ...

The capacity control of a vapor-compression refrigeration system is investigated for three different capacity control schemes. In a hot-gas by-pass control scheme, the refrigerant is by-passed from the compressor and injected back into the suction line to decrease the cooling capacity, whereas in cylinder-unloading scheme, one or more cylinders are unloaded to decrease the refrigerant mass flow...

A research project of the Hamburg University of Technology realizes an open cycle desiccant assisted air conditioning system based on renewable heat sources e.g. solar thermal and heat sinks e.g. shallow geothermal energy. Both advantages of the open cycle process are taken into account, the possible use of a heat sink at higher temperatures and the use of low calorific heat. Moreover, the tota...

In regions with a continental climate, refrigerators air-cooled condensers operate at high condensation pressures during the summer season which reduces their efficiency and accelerates wear of compressors. To reduce pressure, it was proposed to use radiative cooling is way heat removal through planet's atmosphere outer space in form infrared radiation. A refrigerating machine an assembly inclu...

The mechanical compressor on small cooling appliances has considerable energy consumption to the entire vapor compression system. To improve the efficiency of the compressor in the vapor compression system, an electrochemical compressor (EC) was suggested and its performance was investigated. The EC compresses refrigerant by charging an external voltage to the membrane electrolyte assembly (MEA...

The cooling efficiency of natural draft dry cooling system (NDDCS) are vulnerable to ambient winds, so the implementation of measures against the wind effects is of great importance. This work presents the combined air leading strategies to recover the flow and heat transfer performances of NDDCS. Following the energy balance among the exhaust steam, circulating water, and cooling air, numerica...