Assignment
System:
Central ventilation (for rooms with mechanically supplied air) with heat recovery (winter only), additional central pre-heating to Ts, central humidification with steam and central cooling in combination with local radiators in all rooms. The ventilation air is cooled centrally and supplied to each room separately, resulting in different conditions for every room that do not always meet the design conditions.
Given:
Outdoor condition: 28 °C – 90 % RH (Relative Humidity)
Indoor condition: 20 °C – 50 % RH (Relative Humidity)
Total ventilation flow rate (m3/h): 30521 m3/h
Total perceptible cooling load (kW): 149.6 Kw
Total latent cooling load (kW): 120.8 Kw
Total cooling load (kW): 270.4 Kw
Assignment: Design in the summer situation
- Calculate the feasible building conditions and draw the process in mollier diagram.
Calculate the slope of the supply process and draw the supply line for all cooled rooms together (combined process). For this you need the perceptible and latent cooling load and the water vapour supply of the cooled rooms. The water vapour supply (kg/s) follows from the latent cooling load divided by the heat of vaporisation. Assume the following supply conditions: temperature of 10 °C and relative humidity 100% (= cooler starting conditions) and draw the supply line through this point.
Now determine the energy balance of the building (only for the cooled rooms) and determine the average building conditions (only for the cooled rooms) that arise. The required relative humidity will never be achieved.
Regarding the temperature, assume the following: If the resulting building temperature is higher than the design temperature of the building, this is referred to as top cooling: the design conditions are exceeded under extreme situations. This is accepted. If the resulting building temperature is lower than the design temperature of the building, higher temperature air should be supplied. After cooling, the air must first be post-heated to the new supply temperature, so that the design indoor temperature is achieved precisely. Indicate in the report whether there is top cooling or a higher supply temperature and, in the latter case, determine the new supply temperature and the capacity of the post-heater. Also draw the new supply line and post-heating in the Mollier diagram.
- Calculate the capacity of the cooler.
- Computing of capacity of post-heating.
