Q1: Radiator of an automobile engine is a __________ type of heat exchanger.

ANS:D - direct contact

the term "direct contact" is not typically associated with the classification of heat exchangers like co-current, cross-current, or counter-current. However, in some contexts, "direct contact" heat exchange refers to a specific type of heat transfer where two fluids come into direct contact with each other to transfer heat. This occurs when one fluid is sprayed, poured, or otherwise introduced into another fluid. For example, in a direct contact condenser, steam is brought into direct contact with a cooling liquid (such as water) to transfer heat and condense the steam. In the case of an automobile radiator, the coolant and the air do not come into direct contact with each other. Instead, heat is transferred from the hot coolant to the surrounding air through the walls of the radiator tubes and fins. This is why the radiator of an automobile engine is typically classified as a cross-current heat exchanger, as explained in the previous response. Therefore, "direct contact" is not the appropriate classification for an automobile radiator heat exchanger. If you have any further questions or need clarification, feel free to ask!