Positive displacement compressors have crankcase heat to ____.
A. preheat the chilled water for better efficiency
B. prevent refrigerant migration to the compressor
C. preheat the compressor bearings for longer wear
D. minimize condenser subcooling
Answer: B
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Calculate the ultimate BOD of the mixed river and sewerage stream.
The Ganges River, shown in Figure 4.66, has an annual average flow rate of 12,105 m3/s. The average temperature of the Ganges River was reported to be 24.6ºC. The Ganges has become contaminated with raw sewerage and industrial waste so that the dissolved oxygen in the river upstream of sewerage discharges is 4.6 mg/L. Suppose that the raw sewerage that is untreated flows into the Ganges at a rate of 460 m3/s, the temperature is 25ºC, and the dissolved oxygen in the sewerage stream is completely depleted (i.e. DO = 0). How would you develop a plan for improving water quality in the Ganges River? What will be an ideal response?
Geothermal heat pumps will ____________________ heat from the Earth and transfer it to the conditioned space in the winter and ____________________ the heat that is absorbed from the conditioned space in the summer to the Earth.
Fill in the blank(s) with the appropriate word(s).
A semiconductor is a material ________
A) With exactly four electrons in the outer orbit of its atoms B) Determined by other factors besides the number of electrons C) With fewer than four electrons in the outer orbit of its atoms D) With more than four electrons in the outer orbit of its atoms
The best electrical tape to use as a protective overwrap on high-voltage cables is _____.
a. high-temperature silicone rubber b. rubber c. glass cloth d. vinyl plastic