• Title, Summary, Keyword: Air condition(A/C)

Search Result 895, Processing Time 0.067 seconds

Clothing Microclimate and Subjective Sensations by Wearing Long Johns in Mildly Cold Air (겨울철 실내 온도에서 내복 착용에 따른 의복 기후와 주관적 감각)

  • Kim Myung-Ju;Lee Joo-Young
    • Journal of the Korean Home Economics Association
    • /
    • v.42 no.10
    • /
    • pp.91-104
    • /
    • 2004
  • The purpose of this study was to examine the differences of clothing microclimates and the subjective sensations according to age, gender and clothing weight for $19^{\circ}C$ air temperature. This study was done to gain fundamental data related to saving heating energy and to improve health through wearing underwear (long johns) in lower indoor temperatures. The subjects were divided into four groups (6 young males, 5 young females, 6 old males, 6 old females), and our experiment consisted of three conditions; the first condition was wearing long underwear in $19^{\circ}C$ air (19CUW condition); the second condition was without wearing long underwear in $19^{\circ}C$ air (19C condition); and the third condition was without wearing underwear in $24^{\circ}C$ air (24C condition). The experiment showed that the clothing microclimate temperature and humidity was the lowest in the 19C condition and the highest in the 24C condition irrespective of age and gender. The clothing microclimate in the 19CUW condition was not significantly distinguishable from the other conditions. Clothing microclimate temperature and humidity when the subjects responded thermal comfort was $28\~34^{\circ}C$ and $15\~40\%$RH without any significant difference according to age and gender. For the thermal sensation, the 24C condition was regarded as the warmest environment by the four groups, and the next preference was the 19CUW condition (p<0.001). Young females and old males showed a tendency to feel colder than young males and old females. For the thermal sensation of hands and feet, the young groups felt the warmest in the 24C condition and the coolest in the 19 C condition (p<0.001). However, old males felt neutral for the foot thermal sensation without any significant difference between the three conditions. Old females felt neutral for both the hands and feet thermal sensations without any significant difference between the three conditions. Thermal preference was the highest in the 24C condition for the 4 groups. In the 19CUW condition, for the thermal preference, most young males and females responded 'No change'; on the other hand, mea of the old responded 'Warmer'(p<0.001). It was the 24C condition that the 4 subject groups felt the most thermally comfortable. In the 19CUW condition, over $80\%$ of responses of each group expressed satisfaction and in the 19C condition, over $80\%$ of responses of each group, except young females, expressed satisfaction. In conclusion, in view of the clothing microclimate and subjective sensations, the 24C condition was the condition that gave subjects the least cold stress and the best subjective preference. However, the 19C condition and the 19CUW condition was not such a cold stress as to give healthy subjects a thermal burden.

Psychological and Physiological Responses of Occupants Caused by Types of Seat Air Conditioning (좌석시트 공조조건에 따른 착석자의 심리 및 생리적 반응)

  • Kim, Boseong;Kwak, Seung Hyun;Seo, Sang Hyeok;Min, Byung Chan
    • Journal of the Society of Korea Industrial and Systems Engineering
    • /
    • v.38 no.3
    • /
    • pp.14-20
    • /
    • 2015
  • It is important to understand psychological and physiological responses of occupants who seated in a chair in order to shape a comfortable indoor official environment. So it is needed to find out optimal seated conditions. The purpose of this study was to explore optimal condition of seat air conditioning control based on psychological or subjective responses (perceived temperature and comfort sensation) and physiological responses (heartrate variability; HRV). To do this, experimental conditions were designed by the difference of indoor temperature and seat air conditioning temperature. In the experiment 1, seven experimental conditions were designed with one control condition which was not used seat air conditioning system, and six experimental conditions which the difference of indoor temperature and seat air conditioning temperature ($-1^{\circ}C{\sim}-6^{\circ}C$). In the experiment 2, four experimental conditions were designed with one control condition and three experimental conditions ($-3^{\circ}C{\sim}-5^{\circ}C$). In addition, participants' psychological or subjective response was measured by CSV (comfort sensation vote) and PTS (perceived temperature sensitivity) as a psychological or subjective response, and heartrate variability was measured as a physiological response. As a result, in the experiment 1, it was reported that the optimal conditions of seat air conditioning control based on participants' psychological or subjective comfort were from $-3^{\circ}C$ to $-5^{\circ}C$ experimental conditions. In addition, in the experiment 2, it was reported that the optimal condition of seat air conditioning control based on participants' physiological comfort was $-4^{\circ}C$ experimental condition. These results suggested that seat air conditioning could affected to comfort sensation of occupants in an appropriate range, rather than unconditionally.

Comparison of Condenser Characteristics Using R407C and R22 on the Same Inlet Temperature Condition (동일한 유입온도조건에서 R407C와 R22 적용 응축기의 특성비교)

  • 김창덕;전창덕;이진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.15 no.7
    • /
    • pp.595-603
    • /
    • 2003
  • R407C is considered as an alternative refrigerant to R22 for air conditioners. An experimental investigation was made to study the characteristics of the condensation heat transfer and pressure drop for R407C flowing in a fin-and-tube heat exchanger used for commercial air-conditioning units. Experiments were carried out under the conditions of inlet refrigerant temperature of 6$0^{\circ}C$ and refrigerant mass flux varying from 150 to 250 kg/$m^2$s for refrigerant side. The inlet air has dry bulb temperature of 35$^{\circ}C$ , relative humidity of 50% and air velocity varying from 0.8 to 1.6 m/s. Experiments show that air velocity increased by 25% is needed for R407C than that of R22 for subcooling temperature of 5$^{\circ}C$, which resulted in air-side pressure drop increase of 28.8% for R407C as compared to R22. As a consequence, in order to provide the same design condition of a condenser, the fan requires higher electric-power consumption with R407C than that with R22.

An Experimental Study on Condensation Characteristics at Various Condensation Pressure of R407C (응축압력 변화에 따른 R407C의 응축특성에 관한 연구)

  • 전창덕;장경근;김창덕;이진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.15 no.3
    • /
    • pp.230-238
    • /
    • 2003
  • R407C is considered as alternative refrigerant of R22 for air conditioners. Experimental investigation is made to study the condensation heat transfer characteristics of slit fin-tube heat exchanger using alternative refrigerant, R407C. Experiments are carried out at condensation pressure of 2110 kPa and 1943 kPa with the degree of superheat of 1$0^{\circ}C$ and mass flux varying from 150 to 250 kg/$m^2$s for refrigerant side. The inlet air condition is dry bulb temperature of 35$^{\circ}C$, relative humidity of 50% and air velocity varying from 0.8 to 1.6 m/s. Experiments show that pressure drop gets smaller at a higher condensation pressure especially when condensation pressure is raised from 1943 to 2110 kPa. Heat transfer rate gets smaller at a lower condensation pressure in the range of experimental condition.

A Study on the Three-Dimensional Steady State Temperature Distributions and BOR Calculation Program Development for the Membrane Type LNG Carrier (Membrane Type LNG선의 3차원 정상상태 온도분포 및 BOR 계산 프로그램 개발에 관한 연구)

  • 이정혜
    • Journal of the Korean Society of Marine Engineering
    • /
    • v.23 no.2
    • /
    • pp.140-149
    • /
    • 1999
  • This study is on the development of the computer program that calculates a 3-D hull temperadistribution and analyzes BOR(Boil off rate) to be important to the heat design of a membrane type LNG carrier. The quarter of a tank is taken as an calculation model. And the thermal conductivity of insulation is assumed to be the function of a temperature. In the present steady state calculation, the temperature of LNG in a cargo tank is assumed to be -$162^{\circ}C$ and the air temperature of a cofferdam, to be +$5^{\circ}C$. The lowest air temperature in compartments is calculated as $21.39^{\circ}C$ under the USCG condition ($T_{air}=-18^{\circ}C,\;T_{sw}=O^{\circ}C)$ and B.O.R value is O.0977%/day under the maximum boil-off condition, IMO IGC ($T_{air}=45^{\circ}C,\;T_{sw}=32^{\circ}C$), which satisfies the requirement by KOGAS. The calculated temperature distribution over tank panels at each condition is maximum 3% less than GTT's results. From the results of this study, it can be concluded that the present design of LNG cargo tank satisfies the requirement by KOGAS.

  • PDF

Study on the Performances of Air Flow Fate Effect on a Structured Packed Tower at Adiabatic Condition in a Liquid Lithium Chloride Cooling System

  • Bakhtiar, Agung;Choi, K.H.;Kim, J.R.
    • 한국태양에너지학회:학술대회논문집
    • /
    • /
    • pp.404-408
    • /
    • 2009
  • The liquid desiccant air-conditioning system has been proposed as an alternative to the conventional vapor compression cooling systems to control air humidity. The complete system of liquid desiccant air-conditioning system is consisted two main components those are humidifier (regeneration) and dehumidifier. Humidifier part is connected to the load when summer season which is the air condition is hot and humid have to be turned into comfort condition on human. This paper purpose is performances study of air flow rate effect on a structured packed tower on cooling and dehumidifier system using liquid lithium chloride as the desiccant. Experimental apparatus used in this present study is consisted of three components those are load chamber, packed tower and chiller. Load chamber’s volume is $40m^3$, and packed tower dimension is cubic with length 0.4m occupied with packed column. Totally, 15 experimental has done using 5 times repeat on each variable of air velocity that varying on 2m/s, 3m/s and 4m/s with other conditions are controlled. Air inlet initial temperature and relative humidity are set respectively on $30^{\circ}C$ and 52%, desiccant flow rate is 0.63 kg/s, desiccant temperature is $10^{\circ}C$ and desiccant concentration is 0.4. The result of this study shows that averagely, the moisture removal rate and the heat transfer rate are influenced by the air velocity. Higher air velocity will increase the heat transfer and decreasing the moisture removal rate. At adiabatic condition the air velocity of 2 m/s respectively is having the higher moisture removal rate acceleration then the air velocity of 3m/s and 4 m/s until the steady state condition.

  • PDF

Evaluation of the Energy Efficiency of the Air Engine (공기 엔진의 에너지 효율 평가)

  • Park, Jaehyeon;Baek, Jehyun
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.23 no.5
    • /
    • pp.494-501
    • /
    • 2015
  • Nowadays, many people are trying to develop eco-friendly engines such as the electric motor and the air engine because the I.C. engine cause a lot of pollutants. Nevertheless of these effort, there are few evaluation and comparison of these engines to conventionally used I.C. engines. Because of this, it is difficult to determine that the eco-friendly engines are really energy saving engines. In this paper, the efficiency of the air engine is calculated. The air engine does not cause environmental pollution problem because it uses "Compressed air". Due to the air engine operated at a low temperature and spark-free condition, this engine can be used in extreme condition for safety. Despite the many advantages of the air engine, there are few analysis on the air engine because of an air engine is low energy density.

Comparison of Condenser Characteristics using R410A and R22 under the Same Inlet Temperature Condition (동일한 유입온도조건에서 R410A와 R22 적용 응축기의 특성비교)

  • 김창덕;이진호
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.15 no.12
    • /
    • pp.1049-1059
    • /
    • 2003
  • R410A is considered as an alternative refrigerant to R22 for air conditioners. An experimental investigation was made to study the characteristics of the heat transfer and pressure drop for R410A flowing in a fin-and-tube heat exchanger used for commercial air-conditioning units. Experiments were carried out under the conditions of inlet refrigerant temperature of 6$0^{\circ}C$ and refrigerant mass flux varying from 150 to 250 kg/$m^2$s for refrigerant side. The inlet air has dry bulb temperature of 35$^{\circ}C$, relative humidity of 40% and air velocity varying from 0.68 to 1.6 m/s. Experiments show that air velocity decreased by 16% is needed for R410A than that of R22 for subcooling temperature of 5$^{\circ}C$, which resulted in air-side pressure drop decrease of 15% for R410A as compared to R22. As a consequence, in order to provide the same design condition of a condenser, the fan requires lower electric-power consumption with R410A than that with R22.

Alteration of Leaf Surface Structures of Poplars under Elevated Air Temperature and Carbon Dioxide Concentration

  • Kim, Ki Woo;Oh, Chang Young;Lee, Jae-Cheon;Lee, Solji;Kim, Pan-Gi
    • Applied Microscopy
    • /
    • v.43 no.3
    • /
    • pp.110-116
    • /
    • 2013
  • Effects of elevated air temperature and carbon dioxide ($CO_2$) concentration on the leaf surface structures were investigated in Liriodendron tulipifera (yellow poplar) and Populus tomentiglandulosa (Suwon poplar). Cuttings of the two tree species were exposed to elevated air temperatures at $27/22^{\circ}C$ (day/night) and $CO_2$ concentrations at 770/790 ppm for three months. The abaxial leaf surface of yellow poplar under an ambient condition ($22/17^{\circ}C$ and 380/400 ppm) had stomata and epicuticular waxes (transversely ridged rodlets). A prominent increase in the density of epicuticular waxes was found on the leaves under the elevated condition. Meanwhile, the abaxial leaf surface of Suwon poplar under an ambient condition was covered with long trichomes. The leaves under the elevated condition possessed a higher amount of long trichomes than those under the ambient condition. These results suggest that the two poplar species may change their leaf surface structures under the elevated air temperature and $CO_2$ concentration condition for acclimation of increased photosynthesis.

Attachment of the Air Heat Exchanger for COP Improvement in the Heat Pump (열펌프 성능향상을 위한 공기 열교환기 부착효과)

  • 노정근;송현갑;박용규
    • Journal of Biosystems Engineering
    • /
    • v.27 no.3
    • /
    • pp.235-240
    • /
    • 2002
  • Performance of the heat pump with attaching an air heat exchanger was investigated in the heating condition when the air heat exchanger was worked in the ambient air temperature of -5 to 11$\^{C}$ and air flow rate of 542 to 747 ㎡/h. Performance tests for heating condition were conducted in an experimental room equipped with heat pump. The performance tests were performed in a ambient temperature of -4 ∼ 11$\^{C}$, and room temperature of 4∼22$\^{C}$ respectively. Measured data(temperature, capacity of heat transfer and consumption of electronic power) were analyzed to the efficiency of HEEVA(Heat Exchanger fur the Evaporator), overall heat transfer coefficient and COP of heat pump. The results of inlet temperature for evaporator increased that the temperature was 2 ∼6$\^{C}$, and inlet temperature for condenser decreased that the temperature was 3 ∼ 8$\^{C}$. The results of comparing efficiency of HEEVA for the ratio of heat exchange between hot air and cold air showed that efficiency were considered to 91% because of the ratio of 83∼98%. The results of comparing of COP for the heat pump increased that improvement COP was approximately 0.3∼7.5 than HEEVA had not been operated.