The exhaust air from a building is at a temperature of 22 °C and has a flow rate of 4 kg/s (specific heat capacity of 1.
Posted: Sun May 15, 2022 10:29 pm
The exhaust air from a building is at a temperature of 22 °C and
has a flow rate of 4 kg/s (specific heat capacity of 1.005
kJ/kg-K). A thermal wheel is proposed to recover energy from this
exhaust air to preheat the incoming fresh air at a flow rate of 4.5
kg/s and temperature of 10 °C (specific heat capacity of 1.005
kJ/kg-K).
Given the information determine:
i) The effectiveness of the thermal wheel
ii) The actual heat transfer rate
iii) The exit temperature of the fresh air leaving the thermal
wheel
iv)The exit temperature of the fresh air leaving the wheel if
the speed is doubled.
Data:
Specific heat matrix material = 0.4 kJ/kg-K
Wheel speed = 15 rev/ min
Width of the wheel = 0.2 m
Face area for the wheel = 1.2 m2
Mass of the thermal wheel = 26 kg
Heat transfer coefficients for each air streams = 20 W/m2-K
Matrix surface area to volume ratio = 3000 m2/m3
has a flow rate of 4 kg/s (specific heat capacity of 1.005
kJ/kg-K). A thermal wheel is proposed to recover energy from this
exhaust air to preheat the incoming fresh air at a flow rate of 4.5
kg/s and temperature of 10 °C (specific heat capacity of 1.005
kJ/kg-K).
Given the information determine:
i) The effectiveness of the thermal wheel
ii) The actual heat transfer rate
iii) The exit temperature of the fresh air leaving the thermal
wheel
iv)The exit temperature of the fresh air leaving the wheel if
the speed is doubled.
Data:
Specific heat matrix material = 0.4 kJ/kg-K
Wheel speed = 15 rev/ min
Width of the wheel = 0.2 m
Face area for the wheel = 1.2 m2
Mass of the thermal wheel = 26 kg
Heat transfer coefficients for each air streams = 20 W/m2-K
Matrix surface area to volume ratio = 3000 m2/m3