• Proceedings of the SAREK Conference
• /
• 2004.06a
• /
• pp.135-135
• /
• 2004

• Proceedings of the SAREK Conference
• /
• 2004.06a
• /
• pp.136-136
• /
• 2004

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.11
• /
• pp.733-740
• /
• 2011

To analyze the cooling performance in the refrigerator truck according to frost growth, the analytical model of refrigeration system was developed under frost and non-frost condition using EES. The system performance was analyzed with outdoor temperature, storage temperature, outdoor front air velocity and compressor speed in order to investigate the system performance characteristics with operating conditions. Besides, the system performance under frost condition was compared with that under non-frost condition. As a result, the frost thickness was 0.9 mm when the refrigerating capacity of frost condition was decreased by 30%. The maximum of the system COP was shown at compressor speed of 1500 rpm for non-frost and frost condition, simultaneously. The performance under frost condition was more sensitive to the operating condition compared to that under non-frost condition.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.7
• /
• pp.928-936
• /
• 1999

The electronic refrigerating kimchi jar operates with a low noise because it contains no compressor but it consumes more energy than that of an refrigerator with compressor. In this paper, the heat flow characteristics and cooling performance of an electronic refrigerating kimchi jar are studied by means of experiments. When the storage temperature is kept in a range of $-5.7^{\circ}C$ to $4.1^{\circ}C$. in the case of three ambient temperatures; $12.7^{\circ}C$, $22.3^{\circ}C$ and $32.2^{\circ}C$, the cooling performance of $20{\ell}$ kimchi jar is investigated. The experiments show that the temperature difference that exists between kimchi jar and its ambient provides a measure of the coefficient of performance of kimchi jar. It is also found that ratio of net pumping heat to the heat pumping rate of thermoelectric module is independent of the temperature difference.

• Proceedings of the SAREK Conference
• /
• 2007.11a
• /
• pp.606-611
• /
• 2007

Pulsation is an inherent phenomenon in reciprocating compressors. It interacts with piping to cause vibrations and performance problems. Indiscriminately connecting to a compressor can be dangerous and cost money in the form of broken equipment and piping, poor performance, inaccurate metering, unwanted vibration, and sometimes noise. Piping connected to a compressor can materially affect the performance and response. To minimize these detrimental effects, reciprocating compressor system should be equipped by pulsation suppression system. This study discusses pressure pulsation phenomena occurred in a reciprocating compressor system. An experiment applied air compressor unit, as pulsating pressure generator, has been done. The compressor was connected sequentially to a snubber model and pressure tank. Sensor probes were placed on the inlet and outlet pipes of snubber. Compressor was driven by a motor controlled by a frequency regulator. The experiment was conducted by adjusting the regulator at 40Hz. General information about an internal gas flow can be achieved by numerical analysis approach. Information of the velocity, pressure and turbulence kinetic energy distribution are presented in this paper. Based on this result, the design improvement might be done.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.5
• /
• pp.377-384
• /
• 2012

Vapor injection technique has been applied to prevent performance degrdation of a heat pump at low ambient temperatures. In this study, the heating performance of a heat pump with a variable speed injection scroll compressor using R-410A was investigated by applying sub-cooler vapor injection(SCVI) and flash tank vapor injection(FTVI). The heating performance of the heat pump was measured by varying compressor frequency and outdoor temperature. The heating capacity of the FTVI system was 8~10% higher than that of the SCVI system at all operating conditions. On the other hand, the heating performance improvement with the increase in the compressor frequency was more prominent in the SCVI system than in the FTVI system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.12
• /
• pp.1031-1038
• /
• 2002

The effects of casing shape on the performance and interaction between the impeller and casing in a small-size turbo-compressor are investigated. Numerical analysis is conducted for the compressor with circular and single volute casings from inlet to discharge nozzle. In order to predict the flow pattern inside the entire impeller, vaneless diffuer and casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. For compressible turbulent flow fields, the continuity and three-dimensional time-averaged Wavier-Stokes equations are employed. To evaluate the performance of two types of casings, the static pressure and loss coefficients are obtained with various flow rates. Also, static pressure distributions around casings are studied for different casing shapes, which are very important to predict the distribution of radial load. To prove the accuracy of numerical results, measurements of static pressure around casing and pressure difference between the inlet and outlet of the compressor are peformed for the circular casing. Comparisons of these results between the experimental and numerical analyses are conducted, and reasonable agreement is obtained.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.12 no.4
• /
• pp.184-191
• /
• 2004

In order to improve the performance of a 2 room heat pump with a constant speed compressor, the optimum refrigeration circuit of the heat pump with different cooling and heating capacities is developed by applying capillary tubes. The refrigeration circuit is composed of four parts; a heating circuit, a cooling circuit, a by-pass circuit and a balance circuit. The performance of the 2 room heat pump are investigated from a rating experiment and a reliability experiment, using the calorimeter. Results of the rating experiment show that the capacity of heat pump is about $93\%$ of the design value. In particular, the capacity of the cooling single operation is about $13\%$ higher than the design value, and the capacity of the heating multi operation is about $5\%$ higher than the design value. From the reliability experi-ment, it is found that the lowest driving voltage of the compressor is about $75\%$ of the rating voltage. Also the compressor is reoperated normally under the flood back and the over load.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.4 no.4
• /
• pp.306-315
• /
• 1992

This paper addresses performance analysis of a reciprocating compressor. A computer simulation model has been developed to predict and estimate the compressor performance. Instead of using ideal gas equations, real gas equations are used in describing the state of gas. The compressor simulation model consists of a cylinder control volume, suction system and discharge system. Conservation laws of mass and energy are applied to the cylinder section only, The suction and discharge system are described by the Helmholtz resonator modeling. Some of input data required for the simulation have been obtained from experiments. These experimentally obtained input data are effective flow area, effective force area and dynamic characteristics of valves. Simulation results of real gas equations have been compared with those of ideal gas equations. It has been found that the simulation with real gas equations yields lower cylinder temperature and heat transfer compared with those of ideal gas equations. Differences in pressure, mass flowrates, valve motions and gas pulsations are found quite small.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.22 no.3
• /
• pp.139-148
• /
• 2010

A centrifugal compressor for HFC-134a has been newly designed and developed. Flow analysis using commercial programs was used to evaluate performance and internal flow of the impeller, inlet guide vane and diffuser etc. The purpose of this study is to establish the design theory necessary to the development of HFC-134a centrifugal compressors and to supply basic data related to design by reviewing design values and experimental values through the performance test. The compressor for HFC-134a was also investigated experimentally to check compression performance. The calculated data coincide the test results of compressor. The data obtained in the present study are useful for design of HFC-134a centrifugal compressors.