• Proceedings of the SAREK Conference
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• 2005.11a
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• pp.474-479
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• 2005

For the safe operation of an air conditioner, the liquid car η 'over to compressors should be minimized and compressors should be operated in the specified region of suction and discharge pressures recommended by compressor manufactures. In this study, a capillary assisted tandem-type airconditioner was considered. A variable speed outdoor fan was used to control operating points of the system. Test results showed the possibilities to move system operating points to the safe region by controlling the speed of an outdoor fan.

• Journal of Energy Engineering
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• v.15 no.4 s.48
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• pp.235-242
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• 2006

This study experimentally investigates the performance improvement of the heat pump by adopting the hot gas bypass method and using the internal heat exchanger according to the automatic defrost test conditions of ISO 5151 This study compares the hot gas bypass method with the time step method, and investigates effect on outdoor coil fan speed when the hot gas of compressor outlet enter outdoor coil inlet after the frost formation. The tests were made for the fan speeds of the outdoor coil controlled at 90, 60 and 30% of the normal speed together with the case of the stationary fan. The performance of the heat pump is evaluated by variables such as COP, heat capacity, and the average COP during the 210 minutes heating mode. Results show that average COP of the hot gas bypass mettled is $2.2{\sim}6%$ higher than that of the time step method. When the outdoor coil fan speed is 60% (780 rpm) of the normal speed, it shows the best COP and heating capacity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.3
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• pp.111-118
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• 2017

Performance factors such as the EER(Energy Efficiency Ratio) and the COP (Coefficient of Performance) are being replaced by seasonal energy efficiency factors, like the SEER (Seasonal EER) and the SCOP (Seasonal COP) to evaluate the performance of a heat pump by the time of the year. Seasonal performance factors, such as the CSPF (Cooling Seasonal Performance Factor) and the HSPF (Heating Seasonal Performance Factor) are used to describe the heat pump's performance during the cool and hot seasons. In this study, the optimization of all heat pump's operating parameters was experimentally conducted to enhance the SEER based on the EU standard (EN 14825). Moreover, the SEER was improved by the compressor frequency, as well as indoor and outdoor fan speeds. In addition, the performance characteristics of the heat pump were studied under partial load conditions. As a result, the SEER was enhanced by 17% when the compressor frequency was optimized. An additional 2% improvement was achievable with the optimization of indoor and outdoor fan speeds.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.6
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• pp.517-523
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• 2016

Unlike household refrigerators, commercial refrigerators are composed of separate indoor and outdoor units. The outdoor unit of most commercial refrigerators is designed to run at a fixed speed, which results in low energy efficiency and loud fan noise. Moreover, it cannot respond flexibly to changing thermal load in the indoor unit. Inverter type outdoor units can address such problems through speed changes based on information obtained from the indoor unit. However, using two units from different manufacturers is often not a viable solution. If condition changes in the indoor unit can be detected without communication between the two units, it is possible to adjust the speed of the outdoor unit. This paper attempts to analyze the signal from the outdoor unit when the condition of the indoor unit changes by varying the thermal load.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.3
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• pp.203-209
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• 2003

Control algorithms of an air handling unit by using the mixing box plenum pressures were developed and verified by experiments. Control algorithms developed for this study were the setpoint algorithms for the outdoor damper position, the outdoor/fixed plenum pressure, and the return/exhaust plenum pressure. The outdoor/fixed plenum pressure setpoint was used to control the bypass damper position, and the return/exhaust plenum pressure setpoint was used to control the return fan speed. Experimental results showed the good control of the required outdoor air demand. Therefore, setpoint algorithms developed for this study may effectively be applied for the control of the VAV air handling unit.

• Particle and aerosol research
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• v.15 no.4
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• pp.149-157
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• 2019

Infiltration characteristics of airborne particulate matter had been investigated in real-life for about 90 days over 2 years in a Korean apartment building where a 3-person household had lived and the exclusive private area was 84.9 ㎡. Airtightness was measured by fan depressurization, and the ACH₅₀ was 2.41 times per hour. In and outdoor particle concentrations were measured by optical particle counters. Infiltration factors and filtration efficiencies of the house, which reflect the removal of outdoor particles penetrating building envelope and the deposition inside a building, were obtained from data screened based on an empirical evaluation process. Infiltration factor of fine particles showed a range from about 42% at 0.4 m/s of wind speed to 72% at 4.2 m/s of wind speed with closed windows and doors. Filtration efficiency was like a MERV 13 grade filter with an open window outside at a balcony at low outdoor wind speed under 1 m/s. The grade decreased to MERV 11 by opening another outside window at the other balcony. Filtration efficiencies decreased as much as 29% in average at a range of 0.3~2.5 ㎛.

• Proceedings of the SAREK Conference
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• 2005.06a
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• pp.37-37
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• 2005

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.1
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• pp.16-23
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• 2018

PM synchronous motor may be rotated to an arbitrary direction and speed by outside wind under natural condition in cases where the fan is applied outside, such as in vehicle radiators and outdoor air-conditioners. Sensorless controls that cannot detect rotor position requires additional sensorless control algorithm because a rotor is rotated by an external load. In this study, the sensorless control of a PM synchronous motor under naturally rotating condition is proposed. The natural rotation conditions are classified as forward high-speed rotation, reverse high-speed rotation, and low-speed rotation. Experiment results verify the performance of the sensorless control, including the rotor speed and position detection at natural rotation mode and switch to the closed-loop sensorless control.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.3
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• pp.243-249
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• 2005

The present study has been conducted to simulate dynamics of a gas engine-driven heat pump(GHP) for design of control algorithm. The dynamic modeling of a GHP was based on conservation laws of mass and energy. For automatic control of refrigerant pressures, actuators such as engine speed, outdoor fan, coolant three-way valves and liquid injection valve were PI or P controlled. The simulation results showed physical behavior that is realistic enough to apply for control algorithm design.

• Journal of Bio-Environment Control
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• v.21 no.2
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• pp.79-87
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• 2012

This research was conducted to obtain basic data with regard to the heating performance that would be produced by installing an aluminum hot water pipe inside the greenhouse with the goal of reducing the heating energy in greenhouse. The research results are summarized as follows. The degree of difference in relation to the temperature by height within the greenhouse during the entire experiment was significant - within the range of 4.0~$7.0^{\circ}C$. The temperature difference between incoming and outgoing water was about $3.3^{\circ}C$ greater when FCU was activated compared to when it was not activated. Meanwhile, the amount of energy consumed increased about 36.2~40.1%. The amount of pyrexia per hour also increased by 44.6~52.0%. During the experiment period, circulated flux was within the range of 0.48~$0.49L{\cdot}s^{-1}$ while average fluid speed was 1.53~$1.56m{\cdot}s^{-1}$. The average temperature difference between incoming and outgoing water was 6.24~$11.50^{\circ}C$. The amount of heating value by each set temperature within the minimum outdoor temperature range of -14.0~$-0.6^{\circ}C$ was 135,930~307,150 kcal, and the range was within the 9,610~$19,630kcal{\cdot}h^{-1}$ per hour. This demonstrated that about 23~53% heating energy of the maximum heating load could be supplied. Total radiating value and amount of energy consumed were 2,548,306 kcal and 3,075.7 kWh, respectively. When heating takes place using oil, which is a fossil fuel, the total amount of light oil consumed was 281.6 L while the cost was 321,000 won. When the electricity cost for farms is applied, the total cost was about 110,730 won, which is about 33.5% of the cost required compared to oil consumption. The temperature at in the experiment area was about 8.3~$14.6^{\circ}C$ higher compared to that of the control area.