Abstract:

In order to accurate understanding the system principle of sweating guarded hotplate and relative measurement standards for researchers and users, the design features of two typical sweating guarded hotplates of SGHP and M259B in the world were analyzed. The principles of measurements especial for Isothermal and non-isothermal evaporative resistance under relative standards were expounded. The data of thermal resistances and evaporative resistances with isothermal or non-isothermal of 20 pieces of fabrics were measured by SGHP-10.5. The results showed that the thermal resistance were very similar between two standards with  setp difference of air temperature, while the isothermal evaporative resistances were generally higher than of non-isothermal evaporative resistances by the average17.7% ,which is resulted from hypothesis of the same values of thermal resistance in dry state and moisture absorbed in non stepless method of non-isothermal evaporative resistance measurement. By comparing with measured data of M259B in literature, the different of bare plate data is great, deducing a relative big system error exists in that M259B compared with SGHP-10.5.

Key words: fabric, thermal resistance, evaporative resistance, sweating botplate, system error