FAT 2 – Connection between local and overall thermal comfort: an investigation of the combination effect of seat heating and radiant heat transfer for the purpose of energy-efficient vehicle air conditioning

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Project duration:

12/2013 to 12/2014


Forschungsvereinigung Automobiltechnik e.V. (FAT)


The results of the first FAT-study (see project FAT1) showed a deficit in the design of energy-efficient climate control concepts using a single heating system close to the body. Due to the high complaint rate (> 35%), the seat heater was found to be insufficient as the only measure to compensate for the cool/cold temperature sensation regarding the occupants’ entire body in the case of lowered cabin air temperatures.

To improve the thermal acceptability, the heated seats were supplemented by further heating systems such as a heated steering wheel and different surface radiation elements, which take effect close to the human body. Subject studies served to examine the influence of the combined climate-conditioning systems on the aspect of thermal ergonomics. For the sake of comparative results concerning the energy consumption, the electric capacity of the individual heating systems was measured at the same time.

For the experiments, three identical replicas of a vehicle cabin were built (only for the driver) and equipped with the heating system and various sensors. All in all, twelve test scenarios were performed – accompanied by assessing the subjects’ thermal ergonomics for individual body segments (locally) and the entire body (global). This was done based on the rating scales of ISO 10551 and using an electronic questionnaire for tablet PCs (Android OS, supporting voice command and a touch-function) which was developed by the Institute for the purpose of illustration and assessment.

The results of the evaluation of thermal comfort show that a uniform distribution of the applied heat (in addition to the seats) leads to a significant improvement of thermal comfort, especially regarding the occupants’ body periphery (hands, feet). The heated steering wheel proved to be a particularly effective measure. The results were published in the FAT-Series.