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How to model condensing gas-fired DHW tank in TRNSYS?

asked 2020-10-20 16:33:38 -0500

langeeri gravatar image

updated 2020-10-22 16:55:11 -0500


I am about to be modelling condensing gas water heater used both for DHW and space heating (DHW priority) in TRNSYS for my master thesis. I only had TRNSYS classes during one semester so please be patient with me.

Currently I am waiting for TRNSYS licence from university, so I am preparing at least "theoretically".

I was trying to find Types (in TRNSYS library overview in pdf) which I would like to use in simulation (pumps, Types for underfloor heating, controll etc..) and I couldn´t find any Type, which would allow me to simulate condensing gas water heater. My gas water heater should be tank-type directly heated condensing gas water heater (so I need internal heat exchanger, through which flue gas would flow and heat the water). I found Type60, which has internal heat exchanger, but I don´t know, if this type will allow me to somehow connect the burner and combustion chamber and simulate flue gas flow with possible condensation, if the temperature conditions allows it to condensate. Can anyone give me some advice, what is the best way to simulate this? Thank you all for replies!


Not to be rude, but so far it seems to me that TRNSYS favors solar collectors over gas type heaters :)

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answered 2020-10-21 15:03:57 -0500

Tim McDowell gravatar image

The internal heat exchangers in the tank models in TRNSYS are intended for situations where hot liquid is circulated inside the heat exchanger and not gases. It might be possible to modify the heat transfer parameters to approximate the process with gases.

The tank models in the TESS Storage Tank Component Library include the ability to specify the overall heat loss coefficient (UA) from the specified tank node to the gas flue temperature (which is an input). The auxiliary energy input to the tank can also be specified per tank node.

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Asked: 2020-10-20 16:26:18 -0500

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Last updated: Oct 21 '20