The heat transfer process between body and its ambient is

The heat transfer process between body and its ambient is governed by an Intemal Conductive Resistance (ICR) and an External Convective Resistance (ECR). The body can be considered to be a lumped heat capacity system is

1. ICR > ECR
2. ICR is marginally smaller than ECR
3. ICR = ECR
4. ICR is negligible

Lumped heat capacity can be applied when Bi < 0.1
B_i hl/k, for desired condition i.e. Bi < 0
k > h, ICR is small