• International Journal of Air-Conditioning and Refrigeration
• /
• v.13 no.1
• /
• pp.1-10
• /
• 2005

Screw compressor chillers are widely used in refrigeration for capacity over 30 RT. In general, chillers operate under part-load conditions during most of the time. Therefore, information on the characteristics of part-load is very important for better chiller performance and energy economy. In this study, performance tests of screw chiller with economizer using R22 and R407C under part-load conditions have been performed for various secondary fluid temperatures. Adoption of an economizer system increased the cooling capacity and improved COP except for lower part-load condition when economizer volume ratio is 1.01. For the same cooling capacity condition at part-load, COP's of both non-economizer and economizer system showed similar values.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.11
• /
• pp.902-909
• /
• 2003

Screw compressor type chillers are widely used in refrigeration for capacity over 30 RT. In general, chillers operate under part-load conditions. Therefore, information on characteristics at part-load is very important in view of chiller performance and energy economy. In this study, performance tests of part-load and economizer system using R22 and R407C have been performed for various secondary fluid temperatures. Adoption of an economizer system increased the cooling capacity and improved COP except for lower part-load condition when injection volume ratio is 1.01. For the same cooling capacity condition at part-load, COP of both non-economizer and economizer system showed similar values.

• Journal of Power System Engineering
• /
• v.6 no.2
• /
• pp.68-72
• /
• 2002

Design of experiment was applied to analyze the shrinkage characteristics of the bobbin molded by injection molding. Among lots of design and processing conditions, the thickness of a bobbin and cooling conditions of a mold were considered. The temperature difference between top and bottom parts of the bobbin was considered as the objective to minimize the shrinkage of a bobbin. Optimal thickness of a bobbin was 2.0mm at the part of body and 1.5mm at the part of wing, respectively. Optimal cooling conditions such as cooling time and coolant inlet temperature were 12 second and $12^{\circ}C$, respectively.

• Transactions of Materials Processing
• /
• v.14 no.3 s.75
• /
• pp.233-238
• /
• 2005

Blow molding is divided into three categories, injection stretch blow molding, injection blow molding, and extrusion or direct blow molding. Extrusion blow molding has been studied experimentally to characterize the blowing behavior of parison. Blow conditions such as blowing temperature and cooling time were the experimental variables in this blowing experiment. Wall thickness of the lower part of blow molded sample was thicker than that of the upper part because of the sagging of parison during extrusion process. As temperature increases the wall thickness and the weight of blow molded sample decreased. No thickness variations in the blowing sample were observed according to the cooling time. The lower part of the sample showed high degree of crystallinity compare with the upper part of the sample. Thus the lower part of the sample was strong mechanically and structurally. It was recognized that the uniform wall thickness could not be obtained by only controlling the operational conditions. Parison variator should be introduced to get uniform wall thickness of parison and subsequently produce uniform wall thickness of blow molded product.

• Journal of Korean Association for Spatial Structures
• /
• v.16 no.3
• /
• pp.67-78
• /
• 2016

Determining of the shape in the process of design for natural draught cooling tower is very important, because the shape of hyperbolic shell is respond sensitively to dynamic behavior of the whole cooling tower against wind load. In engineering practice, the geometric parameters have been determining based on the natural frequency. This study analyses influence of the tower shell geometric parameters on the structural behavior. For three representative models were selected, they were analyzed based on evaluation of damage by means of nonlinear FE-method. As a result, a hyperbolic rotational shell with the small radius overall was the lowest damage index induced by sufficient capacity of the stress redistribution and thus a wind-insensitive structure.

• Journal of Power System Engineering
• /
• v.17 no.6
• /
• pp.79-87
• /
• 2013

The improvement of cooling efficiency for the cabinet of automatic controller is the most efficient method of it's application. Therefore, this study has been analyzed and investigated the improvement of cooling efficiency and reduction of energy for the cabinet of automatic controller, respectively. So this study was conducted to enhancement of cooling efficiency for the cabinet of automatic controller by making a structure which produces difference of air pressures in the entrance tube of external air. And the structure has capacity of the pyrogen source (PTC elements) to make temperature range from $145^{\circ}C$ to $155^{\circ}C$. Consequently, temperatures of the upper, the lower in the interior of the cabinet of automatic controller and the exhaust part were revealed $28.57^{\circ}C$, $23.38^{\circ}C$and $36.14^{\circ}C$(average temperature of the exhaust part in case of existing method : $45^{\circ}C$) in target test of this study, respectively. It was found that the cabinet of the automatic controller has better cooling ability than the cabinet of automatic controller by using an existing method.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2007.04a
• /
• pp.148-151
• /
• 2007

We made two injectors that were equal to all design except for existence or nonexistence of swirl chamber of fuel part, because we want to find cooling characteristics at the injector face according to existence or non existence of swirl chamber of fuel part. And we set regenerative cooling channel in injector face for protecting injector face for prolonged combustion time. Two injectors were performed hot firing test, and then we compared cooling characteristics of two injectors. Also we compared O/F ratio effects on cooling characteristics and combustion characteristics.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.9 no.6
• /
• pp.59-65
• /
• 2010

This study deals with the characteristic of refrigerant for heat-treatment deformation control of SCM415 steel. The control of heat-treatment deformation must need the progress of production parts for an industry machine. Most of the deformation is occurred on unequal cooling. The unequal cooling is occurred by a property of quenching refrigeration. When a heated metal is deposited in the refrigeration, the cooling speed is so slow in early period of cooling because of occurring a steam-curtain. After more cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for the part of the industry machine by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on the thermal deformation and fatigue strength are also investigated.

• Transactions of the Korean hydrogen and new energy society
• /
• v.29 no.2
• /
• pp.212-218
• /
• 2018

Li-ion battery system is regarded as one of the most potent power sources for electrified power-trains. For the Li-ion battery system to be widely adopted in automotive applications, the performance, safety, and cycle life issues need to be properly addressed. These issues are closely related to the thermal management of battery system. Especially, the effective cooling module design is the core part for the novel battery thermal management system development. In this paper, an experimental approach was carried out as a basic part of comprehensive battery thermal management research. The main goal of this paper is to present a comparison of two cooling systems (air cooling and phase change material (PCM) based cooling) of the unit 18650 battery module. The temperature rise with different battery discharge rate (c-rate) was mainly investigated and analyzed for two types of battery cooling systems. It is expected that this study can properly contribute to providing basic insights into the design of robust battery thermal management system for vehicular applications.

• Transactions of the Korean hydrogen and new energy society
• /
• v.34 no.4
• /
• pp.350-357
• /
• 2023

In this study, the experimental investigation and theoretical analysis were conducted to verify the cooling capacity of the cryocooler used for pre-cooling of hydrogen gas. The effect of the flow rate on a copper pipe attached to the bottom of the cryocooler, which has a coil shape in a hydrogen line, was investigated. Temperature sensors were strategically placed at various positions on the cryocooler to analyze the temperature variations with respect to the flow rate. In this study, the thermal properties of hydrogen for the pressure and temperature were utilized using REFPROP to analyze the cooling capacity of the cryocooler. Based on the experimental results derived from this study, the cooling capacity of the cryocooler for pre-cooling hydrogen gas was considered by calculating the cooling temperature according to the flow rate through theoretical analysis.