Energy usage calculations of heat exchanger
Energy usage calculations of heat exchanger
(OP)
Hi all,
I'm trying to calculate the energy usage of a developmental hybrid ventilation system.
It's a small domestic sized unit with a water/air heat exchanger. Fresh air from outside flows through the unit where it is tempered before entering a room.
I've rigged it up so that air is blowing over the heat ex at 40 l/s. Warm water is flowing through the heat ex at 4 l/min in a closed loop. I'm heating the water with a domestic immersion heater with an energy meter attached to it.
Letting the system stabilise and then run for an hour, if I use Q=mCpDT to calc the energy given to the air crossing the heat ex it is always much higher than the experimental reading I take from the energy used by the water heater. I thought it would be the other way around! I'm pretty sure my flow rates are correct.
Any ideas?
Many thanks.
I'm trying to calculate the energy usage of a developmental hybrid ventilation system.
It's a small domestic sized unit with a water/air heat exchanger. Fresh air from outside flows through the unit where it is tempered before entering a room.
I've rigged it up so that air is blowing over the heat ex at 40 l/s. Warm water is flowing through the heat ex at 4 l/min in a closed loop. I'm heating the water with a domestic immersion heater with an energy meter attached to it.
Letting the system stabilise and then run for an hour, if I use Q=mCpDT to calc the energy given to the air crossing the heat ex it is always much higher than the experimental reading I take from the energy used by the water heater. I thought it would be the other way around! I'm pretty sure my flow rates are correct.
Any ideas?
Many thanks.





RE: Energy usage calculations of heat exchanger
RE: Energy usage calculations of heat exchanger
Thermal losses through ductwork etc should act to increase my energy reading shouldn't they?
I measured the electric heat input using a cheap off-the-shelf power meter, but have checked it using a commercial unit and it's actually quite accurate. What's 'true watts'?
RE: Energy usage calculations of heat exchanger
RE: Energy usage calculations of heat exchanger