Adiabatic boundaries on simulation of a middle-floor apartment

asked 2022-09-22 05:27:12 -0500

sheeku's avatar

Hello!

I'm currently attempting to simulate the behaviour of a middle-floor apartment as a follow-up to previous simulations of an isolated house with the same house plan. Everything remained the same as in the house file, with the only change being that ceiling, floor, west and east exterior walls were set to adiabatic, assuming the temperatures of the adjacent apartments would be similar. North and south exterior walls remained the same and were the only walls with windows.

For the apartment, the indoor temperature reaches around 65ºC at the exact same time it would reach 49ºC on the house, and I'm sometimes getting differences of about 22ºC between the two.

This is obviously incorrect but I don't know how I could simulate an appartment other than implementing the changes I already have. Is there a way to more reliably mimic a real-life situation?

Thanks!

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Comments

1

I'm first alarmed at 49°C in the house! No AC, so naturally ventilated? EnergyPlus? What options/inputs were selected to simulate natural ventilation? If it's only air infiltration (L/s per m2) or similarly ACH per exposed surface area, then I can foresee removing ~2/3 of all outdoor-facing surfaces (from house to apartment) reducing net air exchange rates in equal measure, and so getting consequent increases in temperature.

Denis Bourgeois's avatar Denis Bourgeois  ( 2022-09-26 09:22:05 -0500 )edit

First of all, thanks for your reply. Yes, EnergyPlus and only inputting infiltration (1ACH for the entire house). I am only using AC (through IdealLoadsAirSystem on 3 of the divisions) when trying to get the cooling loads. My objective is to test different retrofit scenarios under heatwaves. The high indoor temperatures is, I believe, because of the epw file I am using which has weather data corresponding to a week during which a heatwave occured (with temperatures getting to 41.5ºC at times). I've tried removing all internal gains and the difference in results isn't significative

sheeku's avatar sheeku  ( 2022-09-29 14:11:02 -0500 )edit

"I am only using AC when trying to get the cooling loads" ... is confusing. Assuming AC is not available (49°C & 65°C when 41.5°C), and constant 1 ACH (regardless of envelope area) ...

  • CASE A hot/dry: adiabatic conditions (instead of outdoors) for 2x walls + 1x roof offers less surface convective and (especially) surface radiative cooling, mainly at night. There is now no cooling from the ground (floor, now also adiabatic). Less envelope surface cooling could explain such a T°C increase.
  • CASE B tropical: 1 ACH (no AC) is really insufficient.
Denis Bourgeois's avatar Denis Bourgeois  ( 2022-09-30 14:58:47 -0500 )edit
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