Key words: thermal comfort; Influencing factors; Test indicators 

1 office chair seat surface thermal comfort 

1.1 the significance of thermal comfort research office chair seat surface 

Chair of the sitting position, necessary furniture, comfort level greatly affects the quality of people's work and. Office chair and close to the body, the hot problem is seat comfort evaluation of a important influence factor, for office chair seat surface most closely contact with human skin. Skin of respiratory function in the very great degree is affected by the cooling performance of the office chair, office chair if the temperature and humidity and physiological function of the body to adapt to bad will influence human thermal comfort, for a long time can cause fatigue, serious still can make the skin suffer from diseases. This is especially true in the summer, from the point of view of healthy and comfortable, the thermal comfort of the chair seat is very necessary. Office chair comfort of science evaluation can provide very important for the design and manufacture of theoretical basis, so how to design out of the office chair with good thermal comfort, is becoming a hot topic in the industry. 

1.2 the status of study on thermal comfort office chair seat surface 

The study of thermal comfort in China starts late, since the late 20th century to the study of the theory of the human body thermal comfort, in recent years, many scholars at home and abroad for the visitors of thermal comfort evaluation method to do a lot of research 

(1) zhou min et al in the thermal comfort evaluation method of the seat, a probe thermometer is used to measure the seat part in contact with the human body temperature, and combining with the tester of subjective feeling, which will be linked to subjective and objective comprehensive evaluation of thermal comfort performance of the seats. 

(2) Liu Zhuofu extracted from the interface temperature characteristic models such as the final contact surface temperature, the average temperature of the maximum rate of change of the contact surface temperature and the contact surface three evaluation index, on the basis of objective evaluation system of seat comfort is established, using the evaluation system of foam material, molding and wooden seats three seats to evaluate, the result indicates that this evaluation system has certain reliability and practicability. 

(3) Liu Weiyi developed temperature testing device, this device consists of two parts, copper cylinder and thermal insulation layer, sense of temperature testing device is used to replace human trials, security can not only save manpower, increase experiment, at the same time can also reduce caused by different testers to physiology, the in the mind of the experiment error, this device is widely acceptable test conditions, and can take the test and repeat test, the measurement stability and small error. 

(4) Tony on car seat local cooling dehumidification was studied, the basis of the principle of fluid mechanics and heat transfer, the problem of seat and human body contact surface high temperature and high humidity is analyzed, according to the relative size of the car seat and human body, establish a calculation model of the seat, using FLUENT software for numerical simulation of the k - E model to solve the temperature field and humidity field, convenient for car seats to make thermal comfort evaluation provides important theoretical basis. 

The factors affecting the thermal comfort of 2 office chair seat surface analysis 

There are many factors that can influence thermal comfort seat surface, through the production process of office chair seat surface and its composition, main seat surface material, thickness, and the form three aspects of influence on the thermal comfort of the seat. One of the most important factor is the surface material, thermal conductivity, permeability and permeability is an important thermal physical measure material thermal comfort index, so the thermal comfort of the seat from the three aspects. 

2.1 seat surface material 

Bridge can be divided into the material surface surface material and seat surface filling material. Common surface of the seat surface materials such as cloth, mesh surface, cortex. Now appeared a kind of single, splicing seat surface is common cloth or leather with net surface, thereby gaining a better thermal comfort. Commonly used filler material is foam, foam is a lot of more phyletic, the main use foam cotton, usually USES the hardness is 70, density of 30,24,16 foaming cotton as filling material. Different density will produce certain effect on the thermal comfort of the seat, the greater the density of sponge, the smaller the gap, air permeability and moisture permeability will be relatively less. 

2.2 seat surface thickness 

Common office chair thickness within the range of 5-15 cm, usually with thin net surface and surface roughness of office chair, office chair thicker cortex. In the summer, people tend to choose thinner on the surface of the seat chair, so the single net surface office chair more and more popular. In the study of thermal comfort, mainly consider the thickness of the filler material, filler material of the same species, the greater the thickness, the heat and moisture permeability, so its thermal comfort is also the worse. 

2.3 surface morphology 

Existing office chair seat surface morphology is more and more complex, especially the leather office chair seat surface forms. Changes of surface morphology can add cent for office chair appearance, not only to thermal comfort at the same time can produce certain effect. When people sit in different shapes, its contact with the seat surface area, pressure distribution is different, so the temperature of the contact person and seat surface will also be different. 

The above three aspects from the Angle of the chair itself on the analysis of the factors affecting thermal comfort, in order to verify this several influence factors and the relationship between the thermal comfort, can be related to the objective test to validate. 

3 office chair seat surface thermal comfort test 

To evaluate whether a chair seat surface has good thermal comfort, not simple subjective evaluation to get alone, still need to carry on the scientific tests, can from the people and the contact area between the temperature and humidity of two indicators for testing. For the human body temperature and humidity are inseparable. Studies have shown that the human body thermal comfort depends largely on the skin temperature of human body. Generally think that the skin temperature reached 34 degrees Celsius, the human body to start sweating mechanism, through the sweat to reach thermal equilibrium. Normally when temperature remains in a very narrow range, skin moisture content is low, and the body's physiological regulatory activities most hours, he is in a state of thermal comfort. When people sit here, the human body need through the secretion of sweat to reach thermal equilibrium, the body, the more need of heat that need the secretion of sweat, the more the contact area of the greater the humidity. When the cooling effect in a seat under a good condition, its final humidity should be lower than the humidity of surface heat dissipation effect is bad. 

Through the experiment on people with seat surface contact area of temperature and humidity data collection, according to Bedford thermal comfort evaluation index and ASHRAE index of thermal sensation subjects subjective evaluation was carried out on the seat surface, can more accurately evaluate the thermal comfort office chair seat surface. 

4 conclusion 

At home and abroad for thermal comfort evaluation research many seats, but the thermal comfort evaluation for office chair seat surface is relatively small, and mainly are tested for temperature, rarely consider the influence of humidity on thermal comfort. Tend to the discomfort of office chair mainly comes from the humidity, temperature often comfort and humidity are closely linked, so you can combine comfort and humidity temperature comfort to explore the thermal comfort of the chair seat. 

reference 

[1] run-ping niu, qi-zhen Chen, pei-hong zhang. The research status and prospect of thermal comfort [J]. Beijing: human ergonomics, 2004, 10 (1) : 38-40. 

[2] Liu Jianxiong fu-chang zhang, li-ming shen. Sitting and seat design ergonomics study [J]. Journal of human ergonomics, 2005. 

[3] Ding Xiujuan Hu Qinhua, Li Kuishan, etc. The human body thermal comfort research progress [J]. Journal of dongguan, dongguan institute of technology, 2007, 14 (1) : 43-47. 

[4] zhou min, Yang yong. The thermal comfort of the seat material and evaluation [J]. Journal of human ergonomics, 2009, 15 (1) : 28 to 30. 

[5] Liu Zhuofu, Mr. Lane, Li Junfu, etc. Seat temperature thermal comfort objective evaluation model to build [J]. Journal of human ergonomics, 2012. 

Author introduction: mei-lan wang (1992 -), female, changshu, jiangsu province, work units, furniture and industrial design institute, nanjing forestry university, officers: students, research direction: human body engineering.