• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.2
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• pp.69-74
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• 2016

Most hot water heating valves for apartments are constant-flow types, which limit the flow rate through an individual household for even distribution of heating water to other households. The constant-flow type is implemented by an on-off control. As a result, heating water is supplied intermittently and hence, indoor air temperature also fluctuates. Returning water temperature is also high, which reduces energy efficiency. To implement continuous feedback control, the indoor temperature dynamics was simulated to fit a measured temperature history by a state-of-the-art physical model. From the model, it was found that the most important disturbance is outdoor temperature and its effect on indoor temperature lasts about an hour. To cope with the slow response and the significant disturbance, a prediction control with proportional feedback is proposed. The control was found to be successful in implementing continuous heating water flow and improved indoor temperature control.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.2
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• pp.91-97
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• 2002

The present study concerns an experiment on the supply-air control in variable air volume (VAV) system with a Pl control logic. A thermal chamber with a Pl control logic is constructed to verify the previously suggested multi-zone model. The stratified thermal model is adopted in the control logic for a thermal chamber cooling test. The effects of taler- mal parameters and control parameters such as supply air temperature and Pl control factor are investigated by implementing the thermal chamber cooling test. The experimental results obtained show that the transient behavior of the air-conditioned space temperature are in good agreement with the simulation results of the stratified thermal model.

• International Journal of Air-Conditioning and Refrigeration
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• v.11 no.1
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• pp.10-16
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• 2003

The present study performs an experimental measurement on transient thermal response of an air-conditioned space by a variable air volume (VAV) system with a PI(pro-portional-integral) control logic. A thermal chamber with a PI controlled VAV unit is constructed to verify the previously suggested stratified multi-zone model. The effects of thermal parameters and control parameters such as supply air temperature and PI control factor are investigated by implementing the thermal chamber test. The experimental results obtained show that transient behavior of the air-conditioned space-temperature is in good accordance with the simulation results of the stratified thermal model.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.8
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• pp.780-786
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• 2001

For the compressor speed control of a multi-type air conditioning system, a fuzzy control algorithm was developed. The sum of zone temperature errors and its derivative were used as input variables, and the compressor speed was selected as the output variable. To test the effectiveness of the control algorithm, one outdoor environmental chamber and four indoor environmental chambers were used. In the chambers the zone temperature step change test and the indoor unit change over test were performed. Test results showed that, for the control of compressor speed, the fuzzy control algorithm was more effective than the conventional proportional control algorithm for the energy conservation.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.12 no.4
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• pp.21-26
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• 2016

In this study, the control strategies of indoor air temperature in floor radiant heating system were researched by computer simulation. The temperature difference based time control method using the difference of indoor set temperature and indoor temperature is compared with the existing On-Off control one for heating control performances. As a result, the temperature difference based time control method shows better thermal environmental characteristics in case of selected operational conditions in comparison with existing control one.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.11
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• pp.1038-1047
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• 2000

The objective of this study is to develop an optimized Artificial Neural Network(ANN) model to predict the descending time of room air temperature. For this, program for predicting room air temperature and ANN program using generalized delta rule were collected through simulation for predicting room air temperature. ANN was trained and the ANN model having the optimized values-learning rate, moment, bias, number of hidden layer, and number of neuron of hidden layer was presented.

• Journal of Bio-Environment Control
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• v.7 no.4
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• pp.311-323
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• 1998

This study was conducted to analyze the temperature characteristics under tunnel type greenhouse to cultivate watermelon in Sungju region. Air temperature of tunnel type greenhouse was descending rapidly after sunset, and the time required the air temperature inside greenhouse nearly reached the outside air temperature was about 2.5 hours. The maximum air temperature in tunnel type greenhouse, in case of high air temperature day, was exceeding 4$0^{\circ}C$ during day time. Air temperature inside greenhouse during night time could sustain about 2~3$^{\circ}C$ higher than the outside air temperature. But it was necessary to supply supplemental heat when the air temperature was below optimum growth temperature. Soil temperature in the depth of 20cm under soil surface could maintain higher than 2$0^{\circ}C$ and the variation range in a day was 3~5$^{\circ}C$, and the soil temperature descending due to irrigation was about 5~6$^{\circ}C$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.2
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• pp.111-119
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• 2011

Recently, the performances of speed and accuracy are enhanced in machine tools. The high speed of the machine tools usually causes harmful thermal displacements on the objects. To reduce the thermal displacements, machine tools generally adopt oil coolers with precise temperature control function. This study aims at precise control of oil outlet temperature in the oil coolers with hot-gas bypass manner based on PI control logic. The control system was designed for obtaining steady state error within ${\pm}0.1^{\circ}C$ and maximum overshoot with 0.8% even though abrupt disturbances are added to the system. We showed that the PI gains could be easily decided by numerical simulations using practical transfer function which got experiments. Also, transient characteristics could be improved significantly by reflecting the inlet temperature of an evaporator to the output of a controller feedforwardly considering periodic abrupt disturbances. Through some experiments, excellent control performances were established by the suggested control.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.453-458
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• 2011

Air preheater uses the waste heat of the gas which burnt from the boiler from the thermal power plant. Air preheater it is established in the exit of the boiler follows in change of temperature combustion gas and the vibration which it follows in thermal expansion and contraction occurs. Air preheater with ruse the gas the seal the place where it includes a gap in the structure which it does, the vibration which it follows in change of temperature fluctuates the displacement of gap, fluctuation of the leakage quantity which occurs from gap there is a possibility of decreasing an effect to system. Part system it will be able to control the interval of gap in order, control mechanism about under establishing the place where it does the gap control actively, measures a gap the displacement sensor for is necessary. Like this displacement sensor the condition must do continuous running from atmosphere of high temperature was demanded all. This paper investigates the implementation instance of hazard existing which implement the high temperature displacement sensor, it analyzes, produces the result which it examines a model, it was a presentation. These results with the fact that it will contribute in the research for the implementation and a localization of the high temperature displacement sensor and advanced air preheater.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.1
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• pp.77-85
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• 2007

One of the most common approaches to achieve better thermal comfort with the radiant floor heating system is supply water temperature control, which is that supply water temperature is varied with outdoor air temperature. But the application of this control method was not easy, because there has been no way to determine the supply water temperature. So in this study, a comprehensive, yet simple calculation method to find out the required supply water temperature is suggested by combining the building heat loss equation and the heat emission model of hydronic radiant floor heating system for single zone. And then using this calculation method, the multizone control method is suggested and confirmed through the thermal simulation. It is shown that indoor air temperature is stably maintained around the set point.