How does temperature difference affect the rate of heat transfer?

FACTORS AFFECTING HEAT TRANSFER

1. Temperature Difference (.T ) between the two fluids - This is the driving force in heat exchange principles. The greater the .T, the greater the heat transfer rate .
2. Fluid flow rate - Increasing flow rate will increase heat transfer rate.
3. The nature of the heat conducting materials - Some materials have a high conductivity while others don't. This factor is 'built-in' in the design of the Exchanger and choice of materials. It is governed by the design engineers before manufacture.
4. Surface area - The larger the surface area of the conducting interfaces, the greater the heat transfer rate.

The surface area, again, is controlled by the design and manufacture of the exchanger. The more tubes contained in the bundle, the greater the surface area. The tube length will also affect heat transfer, as will the outside diameter and metal thickness of the tubes.