• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.12
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• pp.844-861
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• 2008

The papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during the year of 2007 have been reviewed. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environments. The conclusions are as follows. (1) The research trends of fluid engineering have been surveyed as groups of general fluid flow, fluid machinery and piping, etc. New research topics include micro nano fluid, micropump and fuel cell. Traditional CFD was still popular and widely used in research and development. Studies about fans and pumps were performed in the field of fluid machinery. Characteristics of flow and fin shape optimization are studied in the field of piping system. (2) The research works on heat transfer have been reviewed in the field of heat transfer characteristics, heat exchangers, and desiccant cooling systems. The research on heat transfer characteristics includes thermal transport in pulse tubes, high temperature superconductors, ground heat exchangers, fuel cell stacks and ice slurry systems. For the heat 'exchangers, the research on pin-tube heat exchanger, plate heat exchanger, condensers and gas coolers has been cordially implemented. The research works on heat transfer augmenting tubes have been also reported. For the desiccant cooling systems, the studies on the design and operating conditions for desiccant rotors as well as performance index are noticeable. (3) In the field of refrigeration, many papers were presented on the air conditioning system using CO2 as a refrigerant. The issues on the two-stage compression, the oil selection, and the appropriate oil charge were treated. The subjects of alternative refrigerants were also studied steadily. Hydrocarbons, DME and their mixtures were considered and various heat transfer correlations were proposed. (4) Research papers have been reviewed in the field of building facilities by grouping into the researches on heat and cold sources, air conditioning and air cleaning, ventilation and fire research including tunnel ventilation, flow control of piping system, and sound research with drain system. Main focuses have been addressed to the promotion of efficient or effective use of energy, which helps to save energy and results in reduced environmental pollution and operating cost. (5) Studies were mostly focused on analyzing the indoor environment in various spaces like cars, old tombs, machine rooms, and etc. in an architectural environmental field. Moreover, subjects of various fields such as the evaluation of noise, thermal environment, indoor air quality and development of energy analysis program were researched by various methods of survey, simulation, and field experiment.

• Journal of Bio-Environment Control
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• v.23 no.1
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• pp.11-18
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• 2014

To investigate the influence of surrounding environment on the plant temperature and examine the effect of plant temperature control by fogging and airflow, plant temperature of tomato, inside and outside air temperature and relative humidity, solar radiation and wind speed were measured and analyzed under various experimental conditions in plastic greenhouse with two-fluid fogging systems and air circulation fans. According to the analysis of plant temperature and the change of inside and outside air temperature in each condition, inside air temperature and plant temperature were significantly higher than outside air temperature in the control and shading condition. However, in the fogging condition, inside air temperature was lower or slightly higher than outside air temperature. It showed that plant temperature could be kept with the temperature similar to or lower than inside air temperature in fogging and airflow condition. To derive the relationship between surrounding environmental factor and plant temperature, we did multiple regression analysis. The optimum regression equation for the temperature difference between plant and air included solar radiation, wind speed and vapor pressure deficit and RMS error was $0.8^{\circ}C$. To investigate whether the fogging and airflow contribute to reduce high temperature stress of plant, photosynthetic rate of tomato leaf was measured under the experimental conditions. Photosynthetic rate was the highest when using both fogging and airflow, and then fogging, airflow and lastly the control. So, we could assume that fogging and airflow can make better effect of plant temperature control to reduce high temperature stress of plant which can increase photosynthetic rate. It showed that the temperature difference between plant and air was highly affected by surrounding environment. Also, we could estimate plant temperature by measuring the surrounding environment, and use it for environment control to reduce the high temperature stress of plant. In addition, by using fogging and airflow, we can decrease temperature difference between plant and air, increase photosynthetic rate, and make proper environment for plants. We could conclude that both fogging and airflow are effective to reduce the high temperature stress of plant.

• Journal of Animal Science and Technology
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• v.48 no.4
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• pp.555-562
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• 2006

The objective of this study was to evaluate the effects of dietary cation-anion difference (DCAD) with or without ruminally protected fat and niacin on the thermoregulatory ability, milk yield and milk composition of lactating dairy cows during summer in Korea. Thirty mid-lactating Holstein cows (134±12.4 DIM and 23.4±2.3kg/d of milk yield) were divided into three groups (10 animals/group). Cows were housed in a free-stall barn and were provided with forced- air ventilation (wind velocity = 4 m/s) using 41 cm diameter fans. Diet one was formulated to contain low DCAD (+15 DCAD) while the remaining two diets were higher in DCAD (+30 DCAD). One higher DCAD diet was formulated to contain by-pass fat and the second higher DCAD diet contained the niacin along with by-pass fat. The maximum ambient temperature during July was 28.5℃ which could be seen as a period of mild heat stress. As summer progressed, August was characterized as a severe heat stress condition with maximum ambient temperature (32.4℃) and THI (74.0). Dry matter, crude protein and total digestible nutrients intake was not affected by the DCAD level and supplementation of ruminally protected fat or niacin. Milk production was higher in cows fed diets supplemented with fat and niacin than those fed un-supplemented diet. No difference in milk yield was observed in cows fed diets supplemented with fat or niacin plus fat. Milk fat and rectal temperature were not affected by the DCAD level and supplementation of ruminally protected fat or niacin. However, respiration rate was decreased in cows fed diets supplemented with either fat or fat and niacin compared to those fed. The results of the present study indicated that higher DCAD (+30) and supplementation of fat along with niacin can somehow mitigate the negative effects of heat stress on milk yield and physiology of lactating Holsteins during July and August in Korea. In present study reduced respiration rate and increased milk yield in lactating cows may be attributed to the cooling effect of supplemented fat along with vasodilatory functions of niacin. (Key Words: DCAD, Heat stress, THI, milk yield, Milk fat, Holstein)