Estimation of Thermal and Latent Heat Transfer Rates through Clothes

Abstract

  Thermal and latent heat transfer rates through clothes were estimated with heat and mass transfer coefficients for air gap between clothes, cloth of clothes, lined material and boundary film within surrounding air, respectively. Four sets of clothes were examined – set A: underwear, a shirt-blouse, a sweater and a down coat, set B: underwear, a shirt-blouse, a sweater and a jacket, set C: underwear, a shirt-blouse and a jacket, set D: underwear and a shirt-blouse. The conditions for calculation were a temperature of 33℃ and humidity of 50％ at the skin surface and a temperature of －2～30℃ and humidity of 20～70％ within the surrounding air. Temperatures within the surrounding air at a humidity of 50％ corresponding to the heat transfer rate of 60 W/m² were －2℃ for set A, 12℃ for set B, 17℃ for set C and 24℃ for set D. The ratio of latent heat transfer rate to the total heat transfer rate for set A was 0.18, which was small because of large mass transfer resistance of the cloth used for the down coat. The cloth was taffeta with a volumetric fiber fraction of 0.55 within the cloth. The tortuosity of the air channel within the cloth increased with the increase in the volumetric fiber fraction, and the mass transfer coefficient of the cloth became smaller. The ratios of latent heat transfer rate for set B, C or D were between 0.3 and 0.6, and decreased with the increase in humidity within the surrounding air. The volumetric fiber fraction of cloth used with sets B, C and D was smaller than 0.33, and the mass transfer resistance of cloth was very small in comparison with that of the air gap between clothes as well as the heat transfer resistance. The ratio of latent heat transfer rate for sets B, C and D was close to that for the air gap between clothes.