Question

You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer.

Answer 1

Hint: In order to understand this condition, it is important to understand the principles of heat transfer. The principle behind the mode of heat transfer among the three modes of heat transfer viz. conduction, convection and radiation, that is responsible for this condition must be understood to explain the reason.

Complete answer:
While the subject of thermodynamics gives us the estimation of the heat transferred, the subject of heat transfer deals with the mode in which the heat transfer.
There are three principal modes of heat transfer, viz. Conduction, Convection and Radiation.
Conduction of heat occurs through transfer of energy through vibration of the particles of the medium without actual displacement of the particles of the medium. It mainly occurs in elastic media like solids.
Convection of heat occurs through the actual movement of particles of the medium from regions of high temperature to lower temperature thereby, conveying the heat energy in the process. It occurs in fluidic media like liquids and gases.
Radiation of heat occurs through emission of heat energy in the form of electromagnetic radiation directly from the surface of the body.
The principle of ventilation is based on the concept of convection of heat.
When the air in a room gets heated, it rises up due to lower density. To replace this air, the cold air from the surroundings flows into the room. This pushes the hot air out of the ventilator, a window present near the ceiling of the room. This process of heat removal from the room occurs through convection.
Thus, absence of ventilators in the room does not give room for the hot air to be transferred to surroundings through convection and the hot air lingers in the ceiling. This hot air, eventually, heats up any air entering the room through the windows thereby, causing severe discomfort.
Hence, it is highly advisable while buying a house to ensure adequate ventilators are present. Therefore, a house with no ventilators is not the best choice to buy.

Note: The students should not assume that the heat never escapes the room without the ventilation. The hot air loses temperature slowly, through radiation and conduction, but the process is very slow. This allows very less time for the cooling effect in the house since the cold air entering gets heated up. Thus, ventilator aids in cooling the house faster compared to absence of ventilators, which is really necessary.