I am modelling a building in TRNSYS with radiant cooling panel equipped with DOAS(Dedicated Outdoor air system) .
I need to calculate the cooling load. I calculated the cooling load by using "mcdt", the sensible heat taken by the cooling water in the radiant panel. And the rest is taken by the DOAS(Cooling coil) which is mcdt for sensible load and mLdt for the cooling load.
I want to check the heat gain from the building envelope, the occupants, lighting and the equipment and compare it with the cooling load i calculated.
Can you please suggest me how to find the gain from the walls, occupants,equipments and lighting by using the "built in output Q" in TRNBuild.
Can you kindly suggest me what "Q" value should i use from the TRNBuild output file of Type 56?
Dear Ashmin Aryal ,
I think you can use the balances of Type 56.
In TRNSYS 17, you find them under Outputs -> NTypes -> balances (BAL4: BALANCE 4 - ENERGY BALANCE FOR ZONES). You find also information on this in the manual of the Multizone Building (5.2.3.5.4. for TRNSYS 17). (Don't forget the solar gains from windows). You can run the simulation with ideal cooling to estimate the cooling load to maintain a defined set temperature in the rooms and use the values from BAL4.
I hope this helps you with your work,
Best regards
Danny
@Ashmin Aryal
Im new at TRNSYS so i cant tell you where to look, sorry.
But i want to tell you building heat gain and cooling load is not the same thing because of thermal mass that causes heat transfer delay. So i would recommend you to use TETD/TA, CLTD/CLF or RTS method described in ASHRAE handbook of fundamentals to calculate the cooling load of buildings.
Best regards.
Danny Jonas I have cooled the building by external means with the help of cooling coil (type 752f)(AHU and DOAS). SO, for this case i am planning to use the ENERGY BALANCE FOR ZONES: I am setting B4_QBAL as zero. B4_QHEAT =0 and B4_QCOOL = 0, and just sum up the remaining terms. I think those are the parameters contributing to the cooling load. (i am confused about the negative sign at the begining of the equation)
B4_QBAL =- B4_DQAIRdt + B4_QHEAT - B4_QCOOL + B4_QINF
+ B4_QVENT + B4_QCOUP + B4_QTRANS
+ B4_QGINT + B4_QWGAIN + B4_QSOL
+ B4_QSOLAIR (kJ/hr)
SO the cooling load now will be: - B4_DQAIRdt + + B4_QINF
+ B4_QVENT + B4_QCOUP + B4_QTRANS
+ B4_QGINT + B4_QWGAIN + B4_QSOL
+ B4_QSOLAIR.
I hope this is right. Please correct me if my idea is wrong.
Thank you so much for the reply.
Dear Ashmin Aryal ,
The sign is negative as the balance is:
dQair/dt = sum of all heat fluxes / gains into / from the airnode (1)
(1) can be reformulated as:
0 = - dQair/dt + sum of all heat fluxes / gains into / from the airnode (2)
I'm not familiar with the mentioned types but I think you have to connect the type with the building and use the temperature output of the cooling equipment as temperature of a ventilation into the zone. This energy flux is then part of the ventilation gains balance B4_QVENT (beside other defined ventilation gains).
I think you can set the ideal cooling and then you get the cooling demand / loads from B4_QCOOL. If you use the cooling type, I think you calculate the cooling energy (including e.g. mismatching of set temperatures) that is not equal to the demand.
Best regards,
Danny
the energy balance equation where all the energy coming in and out are written. The equation is (NTYPE 904)
B4_QBAL =- B4_DQAIRdt + B4_QHEAT - B4_QCOOL + B4_QINF + B4_QVENT + B4_QCOUP + B4_QTRANS + B4_QGINT + B4_QWGAIN + B4_QSOL + B4_QSOLAIR [kJ/hr].
I printed this balance as Energy_zone.BAL. When i checked the file B4_QWGAIN is 0 and B$_QSOLAIR is also 0. Why are they zero?
So, I was wondering what B4_Qwgain is? ( I am particularly interested in it because i need to calculate the heat gain through the envelope).
As per what I have read from the manual it says, wall gain is something that is fed by the user (can’t it be calculated by TRNSYS).
My question is how to calculated the heat gain from the building envelope?
I need it because the cooling load that I calculated for my system (CHILLED CEILING + DOAS) is too low as compared to thumb rule calculation.
Danny Jonas
the energy balance equation where all the energy coming in and out are written. The equation is (NTYPE 904)
B4_QBAL =- B4_DQAIRdt + B4_QHEAT - B4_QCOOL + B4_QINF + B4_QVENT + B4_QCOUP + B4_QTRANS + B4_QGINT + B4_QWGAIN + B4_QSOL + B4_QSOLAIR [kJ/hr].
I printed this balance as Energy_zone.BAL. When i checked the file B4_QWGAIN is 0 and B$_QSOLAIR is also 0. Why are they zero?
So, I was wondering what B4_Qwgain is? ( I am particularly interested in it because i need to calculate the heat gain through the envelope).
As per what I have read from the manual it says, wall gain is something that is fed by the user (can’t it be calculated by TRNSYS).
My question is how to calculated the heat gain from the building envelope?
I need it because the cooling load that I calculated for my system (CHILLED CEILING + DOAS) is too low as compared to thumb rule calculation.
Ashmin Aryal
B4_QWGAIN is an additional gain that can be defined within TRNBUILD. It can be used to simulate a heat flow on the inside of the wall. B4_QSOLAIR is the "convective energy gain of airnode due transmitted solar radiation through external windows which is transformed immediately into a convective heat flow", you can define it in TRNBUILD by a so called solar-to-air-factor (fraction of solar heat entering an airnode that is "immediately transferred as a convective gain to the internal air. This fraction depends on the quantity of internal items with very low thermal capacity such as furniture."
So, I think you don't need to define this values for you simulation. As you don't use it, B4_QWGAIN and B4_QSOLAIR are zero. The heat loss through the building envelope by heat transmission through walls, windows, roof etc. is B4_QTRANS. But you have also losses or gains by ventilation and infiltration, B4_QINF and B4_QVENT. But these values can also contain your heating energy if you heat the zones by ventilation for example. So, as mentioned before it depends also on the way you put the energy in the zones.
Best regards
Danny
Danny Jonas thank you so much for clearing this. I was guessing the thing you mentioned but was not sure. thanks a lot.
Ashmin Aryal
I am glad that I could help you. Wish you a good progress in your study!
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