• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.4
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• pp.213-220
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• 2016

The objective of this study is to investigate the cooling performance of an air-conditioning system for a special purpose vehicle under tropical and severe weather conditions. In order to evaluate and compare the cooling performances, the dual refrigeration cycle using R-134a was tested on a special purpose vehicle with various refrigerant charge amounts and indoor temperatures. The cycle was tested considering indoor cooling speed and compression ratio (discharge pressure), and was optimized at the refrigerant charge amount of 1.5 kg and outdoor temperature of $40.0^{\circ}C$. The time to reach indoor temperature of $15.0^{\circ}C$ increased by 86.5% and 38.1%, at the indoor temperatures from $25.0^{\circ}C$ to $32.5^{\circ}C$ and from $32.5^{\circ}C$ to $40.0^{\circ}C$, respectively. In addition, with the increase in indoor temperature from $25.0^{\circ}C$ to $40.0^{\circ}C$, the cooling capacity increased by 7.3%, from 19.1 kW to 20.5 kW, but decreased by 7.0% from 4.67 to 5.1.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.4721-4726
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• 2010

The performance characteristics of water-chilling heat pump using CO2 for the control of inverter frequency was investigated experimentally. An experimental apparatus is consisted of a compressor, a gas cooler, an expansion valve, an evaporator and a liquid receiver. All heat exchangers used in the test rig are counter flow type heat exchangers with concentric dual tubes, which are made of copper. The gas cooler and the evaporator consist of 6 and 4 straight sections respectively arranged in parallel, each has 2.4m length. The experimental results summarize as the following: for constant inlet temperature of evaporator and gas cooler, as mass flow rate, compression ratio and discharge pressure increases with the inverter frequency. And heating capacity and compressor work increases, but coefficient of performance(COP) decreases with the inverter frequency of compressor. As inlet temperature of secondary fluid in the evaporator increases from $15^{\circ}C$ to $25^{\circ}C$, compression ratio and compressor work decreases, but mass flow rate, heating capacity and COP increases with the inverter frequency of compressor. The above tendency is similar with performance variation with respect to the variation of inverter frequency in the conventional vapor compression refrigeration cycle.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.990-995
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• 2009

Experimental basic study was performed to understand the characteristics of sub-cooled refrigerant using a cold heat storage system. This system was made up general vapor-compression refrigeration cycle added sub-cooler and ice storage tank. The purpose of this study are to application use of cold-heat storage systems multiplicity of fields and to understand of sub-cooling system. At the condition using ice storage system, the ice making process was operated during night time by electric power. And then, the refrigerant was sub-cooled using stored cold-heat after being discharged from the air cooling condenser during the day time. Comparing the result at general operation with the operation using sub-cooling system. This study showed the effects of the sub-cooled degree. The cooling performance was increased owing to the sub-cooling of refrigerant during day time, and the compressor consume power was a little decreased. Thus the COP was also increased owing to the sub-cooling of refrigerant.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.2
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• pp.121-128
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• 2012

Improvement in the energy efficiency has been studied of the desiccant cooling system by applying a vapor compression type heat pump to modify the system into a hybrid system. The cycle simulation was performed and the results were compared between a reference desiccant cooling system composed of a desiccant rotor, a sensible rotor and a regenerative evaporative cooler, and a hybrid desiccant cooling system with the sensible rotor being replaced by a heat pump. Though the electric consumption increases as much as the compressor power consumption, the total cooling capacity increases and the thermal energy input decreases by the addition of the heat pump. Therefore, the total energy efficiency can be improved if the increase in the electric consumption can be compensated with the increase in the cooling capacity and the decrease in the thermal energy input. The results showed that the total energy efficiency is optimized at a certain heat pump capacity. When the heat from the CHP plant is used for the thermal energy input, the energy consumption of the hybrid system is reduced by 20~30% compared with the reference system when the heat pump shares 30~40% of the total cooling capacity.

• Clean Technology
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• v.20 no.1
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• pp.1-6
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• 2014

$CO_2$ is generated by the combustion reaction, when getting the energy from fossil fuel. If the carbon dioxide emissions increases more, the global warming problem will become more serious. CCS (carbon capture storage) needs to be developed for the prevention of this. When liquefied $CO_2$ is transported, BOG (boil-off gas) is generated because of several problems. In the study, by injecting liquefied $CO_2$ in two tanks which contains $40m^3$each, the amount of BOG and its composition were measured during 30 days when generating pressure changes and external heat, loading, unloading. In result, 16,040 kg of BOG was generated and the composition has been found out to be 99.95% $CO_2$ and 0.05 % $N_2$. Also, we conducted simulation process for reliquefaction of generated BOG with vapor compression cycle using the PRO/II with PROVISION version 9.2. As a result, the refrigeration cycle of the total circulation flow rate was 42.07 kg/h and the condenser utility consumption was 48.85 kg/h.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.11 no.4
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• pp.1-6
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• 2015

In this study, energy performance of two types of food dryers which are electric heater and heat pump is studied experimentally. With drying chamber temperatures controlled at 45, 50 and $55^{\circ}C$, sliced radish is dried from an initial mass of 90 to final 7 kg. Moisture content, drying time, total power consumption, MER (moisture extraction rate, kg/h) and SMER (specific moisture extraction rate, kg/kWh) are measured and analyzed. As the drying chamber temperature is increased, drying time is shortened but energy efficiency is reduced for both types. For an electric heater dryer, the effect of chamber temperature on drying time is significant but less significant on energy efficiency. For a heat pump dryer, the dependence of chamber temperature on drying time is weak but strong on energy efficiency. Temperature levels have little effect on electric heater dryer performance but strong effect on heat pump dryer which operates on a vapor compression refrigeration cycle. The energy performance of the heat pump dryer is superior with an average SMER of 2.175 kg/kWh which is 2.22 times greater than that of the electric heater dryer with SMER of 1.224 kg/kWh.