2. Find amount of heat removed from skin surface for each liter of sweat that evaporates from the skin. At normal skin temperatures (37º C) the latent heat of vaporization of water is L, = 2.4 × 106 J/kg and density of water p = 998.2 kg/m³. Units of heat are Joules(J) and calories (cal). Relationship between units 1 cal = 4.18 J and 1 Cal = 1000 cal = 4180 J The quantitative relationship between heat transfer Q and temperature change AT contains three factors: Q = mcAT = mc(T, – T2), where Q is the symbol for heat transfer, m is the mass of the substance in kg (m = pV), and AT is the change in temperature. The symbol e stands for specific heat and depends on the material (J/kg-"C). The specific heat is the amount of heat necessary to change the temperature of 1.00 kg of mass by 1.00°C. 2. Energy eliminated during a phase change (vaporization/condensation) is determined by equation: Q = ml.,, where Q is the symbol for heat transfer, m is the mass of the substance in kg pV), latent heat of vaporization L, (J/kg). 1. (m = Solid Metal rod Air convection Radiation Heat flow b Convection c Radiation a Conduction The amount of heat transferred by conduction Qe is given by 3. 0. = KACT; -Tt = hçonductionA ATt, %3D here A is the area of the contact (m²), L it is length (m), and T, – T, is the temperature difference between the two ends ("C ). The constant K, is the coefficient of thermal conductivity (J/m-sec-"C), t is time (sec), heonduction= coefficient of conduction heat transfer (J/m²-sec-"C), d is the thickness of the material (m). Conduction Through Multiple Layers: when more layers are added, we would expect the rate of heat transfer to decrease: htotal hjayeri hiayer2 4. The amount of heat transferred by convection Q. is given by Q = K{Ac(T; – Ta)t, here A, is the area exposed to convective currents (m); T, and Ta are the skin and air temperatures, respectively ("C); K! = 8.3v06 is the coefficient of convection, which is a function of the velocity v of the convective fluid (J/m²-sec-°C), t is time (sec). For air K! = 8.36, here v is air velocity. 5. The amount of heat transferred by radiation Q, () is given by Q, = k,eA, (T – T$)t where T, and T, are the skin surface temperature and the temperature of the nearby radiating surface (K), respectively; A, is the area of the body participating in the radiation (m²); e is the emissivity of the surface;