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Help With Ventilation System

Question asked by Euan Muir in #Mechanical #Civil & Structural on Nov 11, 2020
Euan Muir · Nov 11, 2020
Rank E2 - BEGINNER

Hi there, I am a trainee engineer and I am having trouble with a question that I was given. I am supposed to use the CIBSE Psychrometric chart to help me figure out the answer to the questions below. Could you give me a hand? I am stuck.

• Evaluate and discuss the design of the proposed ventilation system (Figure 2) using the design parameters given in Table 2, by: a. Determining the properties of air at all points in the system b. Drawing all processes on a Psychrometric chart c. Determining the energy required by the Electric Heater
• Discuss and determine any cost savings in using the heat recovery system instead of just a standard electrical heating system to heat the fresh air to the supply temperature.

Posted in: #Mechanical #Civil & Structural
Ramani Aswath · Nov 21, 2020
Rank A1 - PRO

1. Everywhere in the system the RH value is below 100%. This means that there is no condensation. Latent Heat of condensation is not involved.

2. 15000 Cu.m. of air at 28 degC cools to 17 C. Heat loss can be calculated. Take into account the 0.8 efficiency of the heat exchanger.

3. This heat will heat the same volume of incoming air at 5 C. The temperature at point 4 (t C) can be calculated. This has to be raised to 31C by the electric heater. The heat energy and hence the electrical energy can be calculated. The 0.8 efficiency has to be applied again.

4. The heat energy transferred at 2. above can be converted to Electrical energy, which is saved by using this heat recovery system.

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