Show all your work when completing the questions below. Carry your units into each step of your calculations to be awarded a grade.
Compare the cost of running a 100% outdoor air system, to that of a 33% outdoor air system in a home located in two different jurisdictions. The AHU supplies 0.75 kg/s of dry air to a detached home at 18°C, 40% RH (SA). The home measures 190m² (2000ft²) and has 3m ceilings. The outdoor air is 30°C, 80% (OA) and the return air is 24°C, 50% (RA). The cost of energy is $0.10/kWh (North America) and $0.40/kWh (Western Europe). Assume total air pressure is 101,325 Pa and that the enthalpy of the humidifying water is 2510 kJ/kg of water. The mass flow rate of condensate for the 100% outdoor air system is approximately 12.5 grams per second. The mass flow rate of condensate for the 33% outdoor air system is approximately 6.5 grams per second. The AHU operates 6 hours per day.
1. For a 100% outdoor air system
a) Estimate the ACH based on the mass air flow, and geometry, given above? (1 point)
b) How much heat is removed with the cooling coils? (1 point)
c) How much heat is added with the preheating coils? (1 point)
d) How much heat is removed with the cooling coils? (1 point)
e) What is the total daily energy cost for the AHU process if 10% of (Qcool + Qheat) represents the energy is due to fans, pumps, and compressors? (1 point)
For a 33.3% outdoor air system
f) How much heat is removed with the cooling coils? (2 points)
g) What is the total daily energy cost for the AHU process if 10% of (Qcool + Qheat) represents the energy is due to fans, pumps, compressors? (1 point)
Home Investigation
2. Find the barcode of your refrigerator and take a picture of the Manufacturer/Brand, Series Number, Model Number, refrigerant charge and design pressure. (2 points)