Why do commercial refrigeration systems need a defrost system?
What will be an ideal response?
Since most refrigeration systems operate at evaporating temperatures below 32°F, frost will accumulate on an evaporator surface. This frost must be removed on a regular basis; otherwise it will begin to insulate the surface of the evaporator and prohibit the transmission of heat from the product to the refrigerant within the evaporator.
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If the vector diagram of two AC waveforms is a right angle, then the waves _____.
a. are in phase b. are 90° out of phase c. have the same frequency d. have the same peak voltage
Which of the following is an advantage of mechanical filters?
A. New technology B. Extreme flexibility C. Excellent rejection characteristics D. Compatible with larger equipment
Technician A says that the 3 wires on the TP sensor include a 5-volt reference voltage from the PCM Technician B says that a TP sensor is a three-wire variable resistor called a rheostat. Which technician is correct?
A) Technician A only B) Technician B only C) Both technicians D) Neither technician
Which of the following would be considered one of the permittivities of a dielectric material?
A. Gallium B. Copper C. Air D. Silicon