Dong An Cha

A Study on Cooling Characteristics of Ground Source Heat Pump with Variation of Water Switching and Refrigerant Switching Methods

ABSTRACT:The objective of this study is to investigate the influence of the cooling perfor-mance for a water-to-water 10 RT ground source heat pump by using the water switching and refrigerant switching method. The test of water-to-water ground source heat pump was measured by varying the compressor speed, load side inlet temperature, and ground heat source side temperature. The cooling capacity and refrigerant mass flow rate of the heat pump increased with increasing ground heat source temperature. But COP of the heat pump decreased with increasing ground heat source temperature. As a result, the water switching method with counter flow, compared to a refrigerant switching method, improves the cooling capacity and COP by approxi-mately 6～9% in average, respectively.Keywords:Cooling characteristics(냉방특성), COP(성능계수), Ground source heat pump(지열히트펌프), Refrigerant switching(냉매절환), Water switching(수절환) †Corresponding author Tel.: +82-41-589-8528; fax: +82-41-589-8330 E-mail address: kwonok@kitech.re.kr

Experimental Study of Process Chiller for Semiconductor Temperature Control

Key Words: Chamber(챔버), Chiller(칠러), Energy Saving(에너지절감형), Semiconductor(반도체), Wafer Cooling(웨이퍼냉각)초록: 반도체제조를위한공정에서는과도한열이발생한다. 따라서Chamber 내의웨이퍼나주변온도를일정하게유지할수있도록온도의정밀제어가요구된다. 반도체칠러는산업용칠러와는다르게운전조건이24시간년중지속되므로반도체칠러는전력소비량이대단히크며, 냉동기의최적운전제어를통한저소비전력칠러개발이대단히필요하다. 국내에서판매되고있는반도체칠러는수입품에비해전력소비가높아제품경쟁력이낮은실정이다. 이에따라본연구에서는국내에서개발된반도체칠러에관한실험적연구를통하여칠러의부하변화실험, 온도상승하강실험, 제어정밀도실험등을통하여칠러의에너지절감방향을제시하고자한다. 실험을통하여칠러의냉각능력은2.1~3.9 kW, EER은0.56~0.93으로측정되었다. 제어정밀도는0℃에서±1℃, 30℃이상설정에서는±0.6℃로향상되는것으로나타났다.Abstract: Excessive heat may be generated during the semiconductor manufacturing process. Therefore, precise controlof temperature is required to maintain a constant ambient temperature and wafer temperature in the chamber. Comparedto an industrial chiller, a semiconductor chiller’s power consumption is high because it is in continuous operation for ayear. Because of this high power consumption, it is necessary to develop an energy-efficient chiller by optimizing theoperation. The competitiveness of domestic products is low because of the high energy consumption. We experimentallyinvestigated a domestic semiconductor by conducting load change, temperature rise and fall, and control precisionexperiments. The experimental study showed that the chiller had 2.1–3.9 kW of cooling capacity and 0.56–0.93 of EER.The control precisions were ±1°C and ±0.6°C when the setting temperatures were 0°C and 30°C respectively.

Experimental Study on the Control Characteristics of Each Channel in a Semiconductor Chiller

Key Words: Control(제어), EEV(전자식팽창밸브), PCW(냉각수), PWM(펄스폭변조방식), SemiconductorChiller(반도체칠러), Step Moter Operated(스텝모터구동방식)초록: 본연구에서는전자식팽창밸브를적용한반도체공정용칠러에관한실험적연구를통해시스템특성을파악하였다. 또한온도변화에따른신속한대응을할수있도록온도상승및하강실험, 부하변화에따른온도영역별제어정밀도실험을함으로써각제어방식에따른운전특성을파악하였다. 온도상승시소비전력은8.9 kW로측정되었으며CH1이37.5분, CH2가39.5분이소요되었으며, 온도하강에는총26.5분이소요되었다. 부분부하가적용되는경우전부하가적용되는경우에비해제어정밀도의변화폭이큰것으로나타났으며스텝모터구동방식을적용한CH2의제어정밀도가상대적으로우수한것으로나타났다. 냉각수를이용한냉각사이클영역에서소비전력은1.8 kW로냉동사이클을적용한방식에비해절반가량으로감소된것으로나타났다. 본연구는실험결과를바탕으로반도체공정용칠러의최적제어방안을제시하였다.Abstract: The characteristics of a semiconductor chiller system with EEV have been experimentally studied. Threeexperiments on temperature changes (increase and decrease), load variation, and control precision were conducted toinvestigate the operating characteristics of the semiconductor chiller. The power consumption was 8.9 kWduring increase intemperature. The required time was 37.5 min for CH1 and 39.5 min for CH2. Moreover, the time required for fallingtemperature was 26.5 min. The control precision for partial load operation was relatively low compared to that of a fullload operation. In addition, the CH2 equipped with a step motor showed better control precision. The power consumed bythe chiller for process cooling water was 1.8 kW, which was one-half of that consumed during the refrigeration cycle. Theobjective of this study is to provide an optimal control guideline for the semiconductor chiller design.

AN EXPERIMENTAL STUDY OF SEMICONDUCTOR PROCESS CHILLER USING INDIVIDUAL AND DUAL COMPRESSOR METHOD

Excessive heat occurs during the semiconductor manufacturing process. Thus, precise control of temperature is required to maintain constant chamber temperature and also wafer temperature in the chamber. Compared to an industrial chiller, a semiconductor chillers power consumption is very high due to its continuous operation for a year. Considering the high power consumption, it is necessary to develop an energy efficient chiller by optimizing operation control. Therefore, in this study, a semiconductor chiller is experimentally investigated to suggest an energy-saving direction by conducting load change, controlling the temperatures rise and fall and controlled precision experiments. The experimental study shows how the cooling capacity of new model chiller rises over 30% compared to the old model chiller. The time and power consumption in the temperature rising experiments are 43 min and 8.4 kWh, respectively. The control precision is the same as ± 1°C, at 0°C, in any case. However, it appears that the new model channels control precision improves to ± 0.5°C when the setting temperature is over 30°C.

Adsorbent layer for adsorption heat pump prepared with the surface-modified ferroaluminophosphate particles and inorganic silica binder

In this study, we prepared an adsorbent layer for adsorption heat pump by using ferroaluminophosphate (FAPO) particles and inorganic silica binder and characterized the physical properties thereof. We tried two ideas in preparing the adsorbent layer: dual precursor for binder and surface modification of the FAPO particles. The inorganic silica binder was prepared through a sol–gel process by using tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) as the dual precursor. The surface modification by TEOS molecules on the FAPO particles was done to promote the reactivity between particles and binder. The surface modification to form monolayer of silane was carefully done in a hydrophobic solvent, cyclohexane, preventing the supply of water molecules into the solution. As a result, both the use of dual precursor binder and the surface modification effectively improved the mechanical stability of the layer as shown by higher resistance to mechanical vibration. It was analyzed that the addition of MTES served to enhance the mechanical stability of the adsorbent layer by providing the flexible element, Si–C bonding, in the rigid inorganic matrix. To explain the microstructure analysis by SEM and TEM, and the zeta potential measurement, we proposed a surface reaction model comprising the formation of very thin layer of surface silanol on FAPO particles enhancing the reactivity between the particle and the binder. Both the dual precursor and the surface modification produced no noticeable detrimental effect on the key properties such as water vapor adsorption and thermal conductivity.Graphical Abstract

Numerical Analysis of Thermal Environment Control in High-Density Data Center

Increasing heat generation in CPUs can hamper effective recirculation and by-pass because of the large temperature difference between the exhaust and the intake air through a server room. This increases the overall temperature inside a data center and decreases the efficiency of the data centers cooling system. The purpose of the data centers cooling system is to separate the intake and exhaust air by controlling the computer room air-conditioner(CRAC). In this study, ICEPAK is used to conduct a numerical analysis of a data centers cooling system. The temperature distribution and the entire room are analyzed for different volumetric flow rates. The optimized volumetric flow rate is found for each CPU power. The heat removal and temperature distribution for CPU powers of 100, 120, and 140 W are found to be the best for a volumetric flow rate of 0.15 m 3 /s. The numerical analysis is verified through RTI indicators, and the results appear to be the most reliable when the RTI value is 81.

A Study on the Effects of Ceramic Content of CNT / Metal Composite Surface Coatings Fabricated by Cold Spray for Boiling Heat Transfer Enhancement

In this study, the enhancement of boiling heat transfer through surface modification of heat transfer materials by surface coating was investigated. Specifically, the study evaluated how the boiling heat transfer performance of CNT/metal composite coatings, fabricated by the cold gas dynamic spray process, was affected by the addition of different ceramic particles on the raw materials of these surface coatings. These raw materials were composite powders of CNT, Cu powder, and ceramic powders (SiC, AlN, and BN) that were mechanically alloyed using an attrition ball mill.The boiling heat transfer tests were performed in a pool of R134a at a gauge pressure of 2.5 kg/cm2 and liquid temperature of 4.8°C. Test results showed that the addition of ceramic particles in the CNT/Cu composite powders can further augment boiling heat transfer. The augmented boiling heat transfer performance varied with the kind of ceramic powder added and with their quantity. The highest enhancement ratio was 2.57. This was exhibited by a Cu plate specimen that was cold spray coated with (5 vol.% CNT + 95 vol.% Cu) + 20 vol.% AlN composite powder.© 2012 ASME