Mechanical Engineering License Review, Fifth Edition
In 20 chapters, this volume covers the content of the national Mechanical Engineering License Review examination used in all 50 states.
TABLE OF CONTENTS Mechanical Engineering License Review, Fifth Edition
Chapter 17: Heating and Ventilating Text, Questions and Answers
17-1 General Considerations
The concepts of heat transmission we reviewed in Chap. 15 may be applied to the study of the material in this chapter and to the next on air conditioning. Overall heat-transfer coefficients are determined in the same fashion in order to calculate building heat losses. The working substance is the air around us and carries the heat into every corner of the building. The flow of heat takes place at constant atmospheric pressure conditions.
Heating and ventilating problems usually involve maintenance of conditions of temperature and humidity within a building. Essentially a building is a shell for keeping out the weather and permitting a satisfactory indoor climate to be maintained. How much heat must be added to an enclosure depends on the construction and tightness. Light construction increases heat losses; substantial construction, while costing more initially, keeps down the costs of operation and fuel. Flimsy and loose construction encourages air infiltration and results in high heat-load needs. Different types of construction are used in the northern and southern parts of the country, and difference in climate is the governing factor.
HEATING
Heat passes from a region of higher temperature to lower temperature. In cold weather heat is lost by a warm building by radiation, by convection, and by the escape of warm air replaced by the colder outside air.
17-2 Over-all Coefficient of Heat Transmission
In actual calculations standard handbooks list over-all coefficients of heat transmission for walls having actual thickness, the material involved, and the surface...
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