Water at 50°c is routed from one building in which it is generated to an adjoining building in which it is used for space heating. transfer between the buildings occurs in a steel pipe (k = 60 w/m-k) of 100-mm outside diameter and 8-mm wall thickness. during the winter representative environmental conditions involve air at t∞ = -5°c and v = 3 m/s in cross flow over the pipe. a) if the cost of producing the hot water is $0.05 per kw-hr, what is the representative daily cost of heat loss from an uninsulated pipe to the air per meter of pipe length? the convection resistance associated with water flow in the pipe may be neglected. b) determine the savings associated with application of a 10-mm-thick coating of urethane insulation (k = 0.026 w/m-k) to the outer surface of the pipe.

freezing

deposition

condensation

explanation;

melting also called fusion is the process where solid becomes liquid, sublimation is the process where solid becomes gaseous without first changing to liquid, deposition involves change from gaseous to solid state, freezing involves change from liquid to solid, boiling or evaporation involves change of liquid to gaseous state, while condensation is the change from gaseous state to liquid state.

endothermic reactions involves absorption of heat from the surroundings or the environment while exothermic reactions involves loss of heat energy to the surroundings.

in this case, sublimation, evaporation and melting are endothermic reactions (gain energy from the environment) while, freezing, deposition and condensation are exothermic (loss of energy to the surroundings) reactions.