• International Journal of Air-Conditioning and Refrigeration
• /
• v.16 no.4
• /
• pp.124-129
• /
• 2008

Design practice has been made on an oil-less scroll air compressor as an air supply device for a 2 kW fuel cell system where air pressure of 2 bar and flow rate of 120 liter/min are required. Basic structure of the scroll compressor includes double-sided scroll wrap for the orbiting scroll driven by two crankshafts connected to each other by a timing belt. These features can eliminate thrust surface which otherwise would produce frictional heat and jeopardize reliable operation of the orbiting scroll and the scroll element's deformation as well. This study focuses on optimum scroll wrap design; orbiting radius has been chosen as an independent design parameter. As the orbiting radius changes, scroll sizes such as scroll base plate and discharge port diameters change accordingly. Gas compression-related losses and mechanical loss also change with the orbiting radius. With a scroll base plate diameter of 120mm at most and discharge port of at least 10mm, the orbiting radius should be within the range of 2.5-4.0mm. With this range of the orbiting radius, it was estimated by performance analysis that the compressor efficiency reached to a maximum of ${\eta}_c$=96% at the orbiting radius of $r_s$=3.5mm for the scroll wrap height-to-thickness ratio of h/t=5.

• Plant Journal
• /
• v.13 no.1
• /
• pp.37-43
• /
• 2017

This study analyzed the change of gas turbine performance with air temperature decrease by the evaporation cooling system in summer season. Gas turbine performance was tested on the condition that ambient temperature is $29{\pm}1^{\circ}C$. As a result, Air temperature at the compressor inlet was decreased by $4.12^{\circ}C$ after the installation of evaporation cooling system. Decreased air temperature followed by increased air density affected gas turbine performance, Which increased compressor pressure ratio by 0.27, improved compressor efficiency of 0.29 %p, improved gas turbine enthalpy drop efficiency of 0.31 %p, improved the gas turbine efficiency by 0.44 %p, improved electric power output by 4,489 kW. On the other side, the influence of the humidity increase and flow resistance increase was negligible.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.42 no.4
• /
• pp.259-266
• /
• 2006

In this study, the 2-way condensation system was designed applying air-to-air heat pump to dry a marine product such as squid in the winter. And to be made the drying apparatuses by this system, there are two kinds of type, A type, was set a compressor outside of the drying apparatus, B type, was set a compressor in the drying room. And then the variations of temperature in drying room were measured to compare the heating performance of the drying apparatuses between A type and B type at $-6.5^{\circ}C$, outdoor temperature. The temperature of the drying room for B type was increased to $36^{\circ}C$ but the temperature of the drying room for A type was not increased to $36^{\circ}C$, to be increased to $20^{\circ}C$.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.9 no.4
• /
• pp.81-88
• /
• 2005

In order to estimate the gas turbine engine performance precisely, the component maps containing their own performance characteristics should be needed. In this study a component map generation method which may identify compressor map conversely from a performance deck provided by engine manufacturer using genetic algorithms was newly proposed. As a demonstration example for this study, the PW 206C turbo shaft engine for the tilt rotor type Smart UAV(Unmanned Aerial Vehicle). In order to verify the proposed method, steady-state performance analysis results using the newly generated compressor map was compared with them performed by EEPP(Estimated Engine Performance Program) deck provided by engine manufacturer. And also the performance results using the identified maps were compared with them using the traditional scaling method. When the performance analysis is performed at far away operation conditions from the design point, in case of use of e component map by the traditional scaling method, the error of the performance analysis results is greatly increasing. In the other hand, if in case of use of the compressor map generated by the proposed GAs scheme, the performance analysis results are closely met with those by the performance deck, EEPP.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.9 no.4
• /
• pp.536-544
• /
• 1997

This study presents test results of a residential window system air-conditioner using R22 and two potential alternative refrigerants, R407C and R410B. A series of performance tests was performed for the basic and liquid-suction heat exchange cycle in a psychrometric calorimeter test facility. For R407C, the same rotary compressor was used as in the R22 system. However, compressor for the R410B system was modified to provide the similar cooling capacity. The evaporator circuit was changed to get a counter-cross flow heat exchanger to take advantage of zeotropic mixture's temperature glide, and liquid-line suction-line heat exchange cycle was also considered to improve the performance of the system. Test results were compared to those for the basic R22 system.

• Tribology and Lubricants
• /
• v.33 no.2
• /
• pp.37-44
• /
• 2017

A DE-side LBP tilting pad journal bearing of a 1-stage overhung heat-pump compressor in a propylene process exhibited abnormal high-temperature behavior. Its temperature had been relatively high at $78^{\circ}C$ from the beginning of operation. In 2014, after three years of operation, it increased suddenly and reached $103^{\circ}C$. Installing a varnish removal equipment and others managed to stabilize the temperature at $95^{\circ}C$. We undertook a troubleshooting approach for reviewing the comprehensive status and integrity of the temperature design of the bearing. We performed lubrication and heat-balance analysis, based on the design engineering data and documents supplied by the OEM. For the base design data of DE-side TPJB, evaluating the effects of key design variables on bearing metal temperature showed that firstly, increasing the bearing clearance and supply oil flow-rate, and next, changing the oil type, and finally, increasing the machined pad clearance and offset, are more effective in reducing the bearing metal temperature. Furthermore, a clarification meeting with the OEM revealed that an incorrect decision had been made to decrease the bearing clearance to eliminate the SSV harshness issue, while not maintaining a sufficient oil flow-rate. We conducted a detailed retrofit design analysis, wherein we increased the oil flow-rate and bearing clearance by decreasing the preload. We predicted that the bearing temperature would decrease to $63^{\circ}C$ from $75.7^{\circ}C$ even at the rerate condition. Finally, after installing and operating a retrofit replacement bearing in 2015, the bearing temperature stabilized at a low temperature of $65^{\circ}C$. Currently (January. 2017), two year later, the bearing metal temperature remains at $65^{\circ}C$. Therefore, we can conclude that the abnormal high-temperature behavior of the bearing has been resolved completely.

• Journal of Power System Engineering
• /
• v.16 no.5
• /
• pp.55-62
• /
• 2012

Centrifugal compressors are widely used and each operating condition is different. However, it cannot be manufactured according to the every operating condition. In the this study, performance of compressor was evaluated with various rotational speeds of impeller and various stagger angles of diffuser in order to apply a typical model widely. A centrifugal compressor was designed and manufactured based on the design point. On this machines, an experiment was conducted and the performance was predicted at off-design point. The performance prediction was validated with the experimental result and the numerical result. Although the isentropic efficiency on the prediction was slightly lower than that on the experimental result due to the heat loss in the experiment, the pressure ratio was predicted well and also the predicted results were matched well with the numerical results. When the rotational speed of the impeller and the stagger angle of the diffuser were changed together, the compressor can be worked in the high efficiency region and avoided operating in the stall region.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.10
• /
• pp.4308-4313
• /
• 2011

The objective of this study is to investigate the cooling performance of the roof mounted air-conditioning system using electric driven scroll compressor for zero emission vehicles. This air conditioner with air source was used R-134a as a refrigerant and tested under various operating conditions such as refrigerant charge amount and indoor temperature, and compressor frequencies. Experimental results revealed that at all tested compressor frequencies, heat transfer rate of the evaporator increased and the cooling COP increased with the indoor temperature. In addition, the heat transfer rate of the evaporator was over 25.0kW sufficient for the cooling loads of an electric bus.

• Progress in Superconductivity and Cryogenics
• /
• v.15 no.1
• /
• pp.45-50
• /
• 2013

Closed-loop J-T (Joule-Thomson) refrigeration cycle is advantageous compared to common open loop $N_2$ decompression system in terms of nitrogen consumption. In this study, two closed-loop pure $N_2$ J-T refrigeration systems with sub-atmospheric device for cooling High Temperature Superconductor (HTS) power cable are investigated. J-T cooling systems include 2-stage compressor, 2-stage precooling cycle, J-T valve and a cold compressor or an auxiliary vacuum pump at the room temperature. The cold compressor and the vacuum pump are installed after the J-T valve to create sub-atmospheric condition. The temperature of 67 K is possible by lowering the pressure up to 24 kPa at the cold part. The optimized hydrocarbon mixed refrigerant (MR) J-T system is applied for precooling stage. The cold head of precooling MR J-T have the temperature from 120 K to 150 K. The various characteristics of cold compressor are invstigated and applied to design parameter of the cold compressor. The Carnot efficiency of cold compressor system is calculated as 16.7% and that of vacuum pump system as 16.4%. The efficiency difference between the cold compressor system and the vacuum pump system is due to difference of enthalpy change at cryogenic temperature, enthalpy change at room temperature and different work load at the pre-cooling cycle. The efficiency of neon-nitrogen MR J-T system is also presented for comparison with the sub-atmospheric devices. These systems have several pros and cons in comparison to typical MR J-T systems such as vacuum line maintainability, system's COP and etc. In this paper, the detailed design of the subcooled $N_2$ J-T systems are examined and some practical issues of the sub-atmospheric devices are discussed.

• Journal of Institute of Convergence Technology
• /
• v.2 no.1
• /
• pp.38-42
• /
• 2012

A scroll compressor used in the air conditioning in automobile consists of the fixed scroll and the orbiting scroll. Temperature gradient in the scroll compressor during the operation induces the thermal expansion of two scrolls. Therefore, the gap between scrolls in the initial stage is regarded as an important variable in structural design of the scroll compressor. The coupled thermal-stress analysis was carried out for the scrolls of a scroll compressor. The temperatures of major points of two scrolls in the steady states were referred by the literature of C. Lin. The sequentially coupled thermal-stress analysis is utilized to the heat transfer analysis and the thermal expansion analysis. In the thermal expansion analysis, the contact analysis was considered between the fixed and the orbiting scrolls in order to obtain the penetration distance and the contact pressure between two scrolls. The range of deformation was from 44 to $76{\mu}m$ according to the height of the scroll. The maximum penetration distance of $60{\mu}m$ occurred at the top surface of the fixed scroll in the center of the scroll parts.