Test: Comfort Conditions - 2 - Mechanical Engineering MCQ

(i) The total heat loss, Q = sensible heat + latent heat sensible heat depends on convection, radiation and respiration.
(ii) Latent heat depends on evaporation of moisture.
(iii) In summer, evaporative losses are maximum.
(iv) in winter, evaporative losses are zero.

Due to electric fan, temperature difference for convection and evaporation increases. To maintain thermal equilibrium, the body starts perspiring to increase the evaporative loss.

A human body feels comfortable when the air is at 21°C DBT with 56% RH. In general, for summer air conditioning, the RH should not be less than 60% whereas for winter air conditioning it should not be more than 40%.

Comfort chart is drawn between DBT-in x-axis and WBT-in y-axis.

In comfort air conditioning, the air is brought to the required dry bulb temperature and relative humidity for the human health comfort and efficiency, while in industrial air conditioning the inside dry bulb temperature and relative humidity of the air is kept constant for proper working of the machine and for the proper research and manufacturing processes.

Explanation:

Effective temperature 

• It is the temperature of saturated air at which a person or human being would feel the same level of comfort as in the actual environment.
• It includes comfort temperature, velocity, and purity.

Factors affecting the effective temperature

Climatic and seasonal differences

• People living in a warmer region feel comfortable at higher effective temperatures than people living in a colder region.
• In summer the effective temperature is 21.6°C and in the case of winter, the optimum effective temperature is 20°C.

Age and Gender

• Children and old age persons need 2-3°C higher effective temperature in comparison to adults. Same the case is with the women.

Kind of activity

• If a person is involved in the foundry shop, dancing or jogging, etc needs a lower effective temperature in comparison to the person in the rest.

Density of occupants

• Highly densely occupied needs a lower effective temperature in comparison to the less densely occupied.