Why radiator is necessary in car and how it's work

                        The function of the radiator is to reject coolant heat to the outside air. The name radiator is a misnomer because the heat transfer from the coolant to the air is by conduction and forced convection and not of by radiation. The cooling effect in the radiator is achieved by dispersing the heated coolant into fine streams through the radiator matrix so that relatively small quantities of coolant are brought in contact with large metal surface areas which in turn are cooled by a stream of air. It is easier to transfer heat from the water to the metal surfaces than from metal surfaces to air. for the same metal exposure surfaces, the heat transfer from the coolant to fins is as much as eight times faster than the heat transfer from fins to air.


                         Air will require a large surface area of metal than that needed for the water. This additional surface area is provided by fins. Not only that, the additional or secondary heat transfer surfaces are so arranged that some turbulence is generated in air passages which further assists the heat transfer process. In the downflow-type radiator, water flows from top to bottom. The radiator has a supply or header tank at the top and a collector tank at the bottom of the main radiator. The header tank receives hot coolant from the engine, accommodates an expansion of water, and also act as a water reserve against coolant loss. A submerged horizontal baffle is provided to reduce mixing of the incoming coolant with air so that aeration, which impairs the radiator heat transfer efficiency, is avoided. in modern design, a separate header tank is provided for this purpose.



                        In cross-flow type radiator, the hot coolant is supplied to the top of the supply tank, it flows across the radiator and is taken out from the bottom of the collector tank. A separate header tank is usually provided at the upper end of the collector tank to prevent aeration and also provide a coolant reserve.

  • Purpose of the cooling fan in Radiator:-

                The purpose of the cooling fan in the radiators is to maintain an adequate air flow across the radiator matrix or core especially at low car speeds and under engine idling conditions. only at high speeds can the ram effect provide all the necessary air flow. The radiator fan is a significant consumer of power and also a source of the noise. A rising level of noise, increasing power consumption and a tendency to overcool are its three basic disadvantages. A cooling fan for heavy diesel truck can draw as much as 37 HP during high way operation at 1900-2300 RPM. the power consumed by the fan represents a parasite demand on the engine. Therefore, the fan is designed to cool the engine at the lowest possible fan speed when the engine is operating at its highest coolant temperature. This requires modification of radiator design air ducting arrangement and the fan design.
  

No comments