2. Conductionȣ
The best heat-insulating solids own their insulating properties to the air or to other gases contained in cells within the material.õĸȲڿͲϸӵԼľܡ These cells cause the heat to flow through the solid material through a long tortuous passage. ЩϸʹҪͨһ۵ͨʵĹ塣 In addition, the available cross-sectional area of the solid material is much less than the projected area. ⣬ʶĹϿõĺͶӰٵöࡣ Experimental evidence shows that many small unicellular pockets of gas are much more effective than a series of connected cells having the same total volume in giving insulating value to a substance. һڸϾͬľֵϣСڴ嵥ϸȵһϵͨϸЧThere may be considerable variation in the thermal conductivity of any given insulating material because the conductivity depends on its density, the size and number of its air cells, and its absorbed moisture.κθľȲϵĵϵкܴIJ죬ΪϵȡܶȣϸĴСյˮ
6. Fundamentals of industrial Ventilation
ҵͨĻ
In essence this boils down to heat transfer and mass transfer between
the incoming air and air the already within the building.ӱϽڽĿѾڽĿĴȺʹʡ If owing to excessive internal heat production the temperature of the air in the building tends to exceed the specified norms, cooler air is introduced and mixed with the indoor air; the temperature of the air (owning to heat transfer) then remains at the norm. ڽﲿȹർ¿¶涨ָ꣬Ŀҿϣڴȣʹ¶ȱֲ䡣If harmful gases or vapours are released, their concentration is heldwithin specified limits by dilution with the clean incoming air.кӷ屻ͷŵŨȽᱻһΧͨϡ͡
7. Natural Ventilation Fields of Application
ȻͨӦ
The time has long passed when it was necessary to demonstrate the benefits of natural ventilation and justify its application. The proofs were simple and very convincing.ʱѾȥܾ˵бҪȥȻͨĺô֤Ŀԡ They were based on comparisons of mechanical ventilation and natural ventilation. ǻȻͨͻеͨıȽϡ In hot shops where all the emphasis was laid on mechanical ventilation, and natural air change, being regarded as unimportant, was not taken into account at all.
ijеصǻеͨ磬Ȼͨ类Ϊصģûбӵġ It was found in all the tests that the volume of natural air change many times exceeded the volume of mechanical ventilation. ܶԱȻͨĻڻеͨĻ This revealed the negligible role of general mechanical ventilation despite its heavy installation and running costs. ȫĻеͨDzƵĺܴװлѡMechanical ventilation in these cases was best used as a corrective to natural ventilation, in the form of air curtains and local air supply or extraction.Щ£еͨȻͨһȴʩԿĻʽ͵ؿĹӦȡ
9. Comfort and Discomfort벻ʣ
A particular example is the range effect.һرΧӰ졣 When an observer experiences a range of stimuli and is asked to rate them on category scale, he tends to rate them by putting the stimuli from the middle of the range into the central categories of the rating scale.һԱһΧĴ̼ҪǷΪͬΧĵȼڴбΧм䵽ͶĴ̼ࡣ This has been clearly demonstrated in experiments on the acceptability of noise. ѾıĿɽԵʵ顣Subjects exposed to a range of sound levels
建筑环境及设备工程专业英语段落翻?- 百度文库
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