7. Transient Temperature
Some designs require a set amount of time to reach the desired temperature. The following equation may be used to estimate the time required:
t = [(r) (V) (Cp) (T1 - T2)]/Q
t = time (seconds)
r = density (g/cm3)
V = volume (cm3)
Cp = specific heat (J/g °C)
T1-T2 = temperature change (°C)
Q = (Qto + Qtt) / 2 (J/s; Note: 1 J/s = 1 W)
Q(to) is the initial heat pumping capacity when the temperature difference across the cooler is zero. Q(tt) is the heat pumping capacity when the desired temperature difference is reached and heat pumping capacity is decreased. Q(to) and Q(tt) are used to obtain an average value.
Heat loading may occur through one or more of four modes: active, radiation, convection or conduction. By utilizing these equations, you can estimate your heat loads. The resulting information can then be used to select a suitable TEC for your application.