HVAC · Heat-Transfer · Problem 6PDFSolution in PDF ↓
HVAC · Heat-Transfer · Problem 6
Problem & Solution
Video Synthesis
Problem: Heat transfer 6, a 75 KVA transformer with 99% efficiency is located in an electrical room at 70 degrees Fahrenheit.
Given: 3 feet high to feet with and 3 feet depth; 1 KW per 1 KVA; 1 KW of real power, and that is going to be 45 KW of real ...
Approach: The load is resistive and uses 60% of the transformer's capacity.
Calc: The load is resistive and uses 60% of the transformer's capacity.
Calc: So a little bit of a 4A into the electrical world here, but don't worry none of these concepts are to the heat transfer coeffic...
Result: Close this to answer choice, see.
Office Hours
2
Student questions asked in live office hours about this problem
OH 15: HVAC: Heat Transfer #6
Q: I think there's an error in your solution—the volume should be 42 cubic feet based on the given dimensions.
A: Good catch—if you're getting 42 cubic feet and the dimensions support that, you may well be right. Let's verify the geometry and confirm; errors can creep in even in reviewed solutions. If your arithmetic is correct, the volume is 42 ft³ and the rest of the solution follows from there.
OH 85: HVAC: Heat Transfer #6
Q: I can't see how the term 'resistive' tells me the power factor equals one—if the power factor or phase angle isn't given, should we assume it's 1?
A: Probably yes—for PE exam purposes, if no power factor or phase angle is given, assuming unity power factor is a reasonable default. I included this concept because I'd encountered similar problems in practice and wanted to expose you to it, but I may have gone deeper into electrical engineering territory than this exam requires. If the problem says 'resistive,' that's your explicit cue that power factor = 1.