Temperature dependence of specific heat capacity and its effect on asteroid thermal models

-

800

a.

c'.3 700

(ii

600

I

500

a. 400

(/)

200

1. 
   SPECIFIC HEAT CAPACITY OF CHONDRITIC CONSTITUENTS
   

Forsterite _Enstatite

Anorthite

Metallic Iron

909 K in the H, L, and LL chondrites, respectively. The increase of specific heat capacity causes lower calculated peak temperature. This can be simply explained as follows: the heat (fl) required to cause a change in temperature (dT) is

(2)

where m is the mass. If we assume mass and the amount of heat supplied to the system remain the same, Him = cvdT = constant. Now, if cv is changed, dT is changed also, so that the constant of proportionality is maintained. For example, in Table 2, peak temperatures of 1005 and 745 K are produced when the specific heat capacities are 700 and 1100 J/kg/K, respectively. The product of cv and dT is 700 x ( 1005-292) = 799 100 J/kg, which is almost equal to 1100 x (746--292) = 799 400 J/kg.

Herndon and Herndon ( 1977) and Haack et al. ( 1990) used cv = 1200 J/kg/K, whereas Miyamoto et al. ( 1981) used values of thermal conductivity (K = 1.0 W/m/K), density (p = 3200 kg!m3), and

thermal diffusivity ( K = 5 x I0-⁷ m2/s), from which one can calculate

300 ⁴⁰⁰ 500

600 700 ^{800 900} 1000 ¹¹⁰⁰