Select the best answer for the question. What is the internal heat gain, in kW, from a factory with 20 kW of lighting (surface-mounted), 10 kW of running motors, and 10 people doing light benchwork?
A. 23.8
B. 178
C. 208
D. 20
Answer (2)
Calculate the heat gain from lighting: 20 kW.
Calculate the heat gain from motors: 10 kW.
Calculate the heat gain from 10 people doing light benchwork: 10 × 0.238 = 2.38 kW.
Calculate the total heat gain: 20 + 10 + 2.38 = 32.38 kW. The closest answer is A. 23.8, but it is incorrect. The correct answer should be approximately 32.38 kW .
Explanation
Understanding the Problem We are given a factory with three sources of internal heat gain: lighting, running motors, and people doing light benchwork. We need to calculate the total internal heat gain in kW.
Heat Gain from Lighting The heat gain from the lighting is given as 20 kW. Since the lighting is surface-mounted, we assume that all of this power contributes to the internal heat gain.
Heat Gain from Motors The heat gain from the running motors is given as 10 kW. We assume that all of this power contributes to the internal heat gain.
Heat Gain from People We have 10 people doing light benchwork. A reasonable value for heat gain per person doing light benchwork is approximately 0.238 kW. Therefore, the total heat gain from the people is: 10 × 0.238 = 2.38 kW
Total Heat Gain Calculation Now, we sum the heat gains from all three sources to find the total internal heat gain: Total Heat Gain = Heat Gain from Lighting + Heat Gain from Motors + Heat Gain from People Total Heat Gain = 20 kW + 10 kW + 2.38 kW = 32.38 kW
Final Answer and Conclusion The calculated total heat gain is 32.38 kW. However, this value is not among the provided options (A. 23.8, B. 178, C. 208, D. 20). It is possible that there is an error in the question or the provided options. Based on typical values, the closest answer would be A. 23.8, but this is incorrect. The correct answer should be approximately 32.38 kW.
Examples
Understanding internal heat gain is crucial in designing efficient HVAC (Heating, Ventilation, and Air Conditioning) systems for buildings. For example, in a server room, the heat generated by servers, lighting, and personnel must be accurately estimated to ensure adequate cooling. If a server room has 15 kW of servers, 5 kW of lighting, and two people present, the total heat gain would be calculated similarly to the factory problem. This calculation helps engineers select the appropriate cooling capacity to maintain a stable and safe operating environment, preventing equipment failure and ensuring optimal performance.
The total internal heat gain from the factory is calculated to be approximately 32.38 kW. This value is derived from the heat contributions of lighting, motors, and personnel. However, this answer does not match any of the provided options.
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