(i) A pipe carrying steam at about 300°C traverses a room, the air being still at 30°C. The major fraction of the heat loss will be by (a) conduction to the still air (b) convection to the air (c) radiation to the surroundings (d) conduction and convection put together. (ii) A satellite in space exchanges heat with its surroundings by (a) conduction (b) convection (c) radiation (d) conduction as well as convection. (iii) For the same temperature drop in the temperature ranges of 300-400°C the heat flow rate will be highest by (a) conduction process (b) convection process (c) radiation process (d) other factors should be known before any conclusion.

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Chapter6: Forced Convection Over Exterior Surfaces
Section: Chapter Questions
Problem 6.25P
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Model the following heat transfer situations. Specify heat flows and storages. Try to write down the mathematical expressions. (i) Solar heating of the road surface (ii) A steam pipe passing through an open space between two buildings (iii) Heat transfer from a person in a warm room in the cold season (iv) Pressure cooker-warming up-cooling down (v) Pressure cooker-steady conditions (vi) A rod with one end in a furnace and the remaining surface in atmosphere (vii) A wire carrying current, exposed to air (viii) A water heater (electrical) with hot water being drawn out with cold water admission. (ix) Cake being baked in an oven or a fruit placed in a refrigeration (x) A frying pan placed on a stove. 1.2 Choose the correct statement in each question. (i) A pipe carrying steam at about 300°C traverses a room, the air being still at 30°C. The major fraction of the heat loss will be by (a) conduction to the still air (b) convection to the air (c) radiation to the surroundings (d) conduction and convection put together. (ii) A satellite in space exchanges heat with its surroundings by (a) conduction (b) convection (c) radiation (d) conduction as well as convection. (iii) For the same temperature drop in the temperature ranges of 300–400°C the heat flow rate will be highest by (a) conduction process (b) convection process (c) radiation process (d) other factors should be known before any conclusion. (iv) In the cold season a person would prefer to be near a fire because (a) the conduction from the fire will be better (b) the convection will be better if he is near the fire (c) direct unimpeded radiation will provide quick warmth (d) combined conduction and convection will be better. (v) A finned tube hot water radiator with a fan blowing air over it is kept in rooms during winter. The major portion of the heat transfer from the radiator to air is due to (a) radiation (b) convection (c) conduction (d) combined conduction and radiation.
1.1 Model the following heat transfer situations. Specify heat flows and storages. Try to
write down the mathematical expressions.
(i) Solar heating of the road surface
(ii) A steam pipe passing through an open space between two buildings
(iii) Heat transfer from a person in a warm room in the cold season
(iv) Pressure cooker-warming up-cooling down
(v) Pressure cooker-steady conditions
(vi) A rod with one end in a furnace and the remaining surface in atmosphere
(vii) A wire carrying current, exposed to air
(vii) A water heater (electrical) with hot water being drawn out with cold water admission.
(ix) Cake being baked in an oven or a fruit placed in a refrigeration
(x) A frying pan placed on a stove.
1.2 Choose the correct statement in each question.
(i) A pipe carrying steam at about 300°C traverses a room, the air being still at 30°C. The major
fraction of the heat loss will be by (a) conduction to the still air (b) convection to the air (c)
radiation to the surroundings (d) conduction and convection put together.
(ii) A satellite in space exchanges heat with its surroundings by (a) conduction (b) convection (c)
radiation (d) conduction as well as convection.
(iii) For the same temperature drop in the temperature ranges of 300–400°C the heat flow rate
will be highest by (a) conduction process (b) convection process (c) radiation process (d) other
factors should be known before any conclusion.
(iv) In the cold season a person would prefer to be near a fire because (a) the conduction from the
fire will be better (b) the convection will be better if he is near the fire (c) direct unimpeded
radiation will provide quick warmth (d) combined conduction and convection will be better.
(v) A finned tube hot water radiator with a fan blowing air over it is kept in rooms during winter.
The major portion of the heat transfer from the radiator to air is due to
(a) radiation
(c) conduction
(b) convection
(d) combined conduction and radiation.
Transcribed Image Text:1.1 Model the following heat transfer situations. Specify heat flows and storages. Try to write down the mathematical expressions. (i) Solar heating of the road surface (ii) A steam pipe passing through an open space between two buildings (iii) Heat transfer from a person in a warm room in the cold season (iv) Pressure cooker-warming up-cooling down (v) Pressure cooker-steady conditions (vi) A rod with one end in a furnace and the remaining surface in atmosphere (vii) A wire carrying current, exposed to air (vii) A water heater (electrical) with hot water being drawn out with cold water admission. (ix) Cake being baked in an oven or a fruit placed in a refrigeration (x) A frying pan placed on a stove. 1.2 Choose the correct statement in each question. (i) A pipe carrying steam at about 300°C traverses a room, the air being still at 30°C. The major fraction of the heat loss will be by (a) conduction to the still air (b) convection to the air (c) radiation to the surroundings (d) conduction and convection put together. (ii) A satellite in space exchanges heat with its surroundings by (a) conduction (b) convection (c) radiation (d) conduction as well as convection. (iii) For the same temperature drop in the temperature ranges of 300–400°C the heat flow rate will be highest by (a) conduction process (b) convection process (c) radiation process (d) other factors should be known before any conclusion. (iv) In the cold season a person would prefer to be near a fire because (a) the conduction from the fire will be better (b) the convection will be better if he is near the fire (c) direct unimpeded radiation will provide quick warmth (d) combined conduction and convection will be better. (v) A finned tube hot water radiator with a fan blowing air over it is kept in rooms during winter. The major portion of the heat transfer from the radiator to air is due to (a) radiation (c) conduction (b) convection (d) combined conduction and radiation.
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