Zhe Li,
I look at similar energy balances quite often so I suspect there
is not a systematic problem but something wrong in the simulation.
There are a few things to look at.
First, make sure that you have some thermal capacitance in the
liquid loop. This will usually take the form of a buffer tank. The
tank should have enough volume to store at least one timestep of
liquid at whatever flow rate your pump is running.
Second, look at the controls on your flow loop. Type941 is basically
an ON/OFF device; it does not meet a set point temperature but
simply puts its entire current capacity into cooling down (or
heating up) the liquid loop. Under low load situations, this can
dramatically overheat or overcool the liquid loop; the tank above
should help this a lot.
Third, make sure that you are using a reasonably short timestep (1
or 5 minutes). this will allow your system to be controller
appropriately.
When you look at the energy balance, you have to also look at the
beginning and ending temperature of the liquid loop. If it is
significantly different than it was at the simulation start, you
have to account for stored energy in your balance.
Kind regards,
David
On 10/16/2012 08:42, Zhe Li wrote:
Dear TRNSYS users,
Thanks for your time.
I am currently performing a simple
validation of an air source heat pump system. The air-source
heat pump is Type941, and I am using a defined thermal load
(Type682) with an input file (Type9). However, the results I
am getting for the Total Heat Transfer to Liquid from output
option in air source heat pump component is between 2 and 3
times higher than the Heating Load Met from output option in
thermal load. I cannot think of any reason why the generated
energy is significantly higher than the load met. I would
understand if the generated energy is a bit higher than the
load met as there might be heat losses from connected pipes.
Could anyone give me some advices? This is
very important for me to continue my research project.
Thanks very much in advance.
Zhe Li
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