The thermostatic expansion valve in a refrigeration system further opens when the diaphragm flexes downward. With all other conditions being the same, what single condition causes this?
• Thermostatic expansion valve (TXV) operation – how the sensing bulb, diaphragm, and valve pin work together • Superheat – what it means and how the sensing bulb temperature relates to it • Forces on the diaphragm: bulb pressure vs. evaporator pressure vs. spring pressure
• Think about what happens to the pressure inside the sensing bulb when its temperature changes. How does that pressure act on the diaphragm? • Consider which force tends to OPEN the valve and which forces tend to CLOSE it. Which single change would increase the opening force without changing the others? • How does evaporator pressure affect the diaphragm compared to bulb pressure? Do they act in the same direction or opposite directions?
• Identify which side of the diaphragm the sensing bulb pressure acts on, and whether that pushes the valve MORE open or MORE closed. • Confirm how a change in evaporator pressure moves the diaphragm – does it assist opening or resist it? • Distinguish between physically changing the superheat setting (spring adjustment) and changing the actual superheat (bulb temperature) during operation.
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