Natural Convection Condenser:

Air movement on the surface of condenser tubes is by natural convection. Since air comes in contact along the warm-condenser tubes, this absorbs heat from the refrigerant and therefore the temperature of the air amplifies. Hot air being lighter rises up and in its position cooler air from below rises to take away the heat from the condenser. This cycle continues. As air moves very gradually by natural convection, the rate of the flow of heat from the refrigerant to air shall be small. Therefore a natural convection condenser is not capable of rejecting heat quickly. Hence a relatively large surface area of the condenser is needed. Thus the use of this kind of condenser is limited to very small units such like domestic refrigerators. However, it requires very little maintenance.

In the small units, the condenser is set at the rear of the refrigerator cabinets. In general, steel tubes are utilized, steel being cheaper than copper. To enhance the heat-transfer area, wires are welded up to the condenser tubes. These wires offer mechanical strength to the coil as well. In definite designs, widely-spaced fins are utilized. It is essential to space the fins quite broadly to avoid resistance to free (natural convection) air movement on the condenser.

Yet another design is the plate-type. The condenser coil is fastened to a plate. The plate having in contact along the condenser tubes, the surface area of the condenser is enhanced. The plate-type condenser is mounted on the back of the refrigerator cabinet along a small gap among the cabinet & the plate. This gap provides an air- flue effect and facilitates better natural convection air currents.

This is obvious that when locating refrigerators or deep-freezes cabinets along a natural convection condenser set up on the cabinet, adequate care should be taken to permit free air movement. Also they must not be near an oven or any hot location.