[TRNSYS-users] storage tank and time step

[Fred Betz]

Jérémy

The heating rate is independent of the time step.

If you are heating at 10,800 kJ/hr and you are running the system for 0.05 hr (3 minutes) then the aux heater will provide 540kJ per time step. You could also write the 10,800 kJ/hr as 3 kW or kJ/sec.

You are mixing up energy (kJ) and power (kJ/hr).

A good way to understand this is by looking at the starting and final temperature and the mass of the water.

If you want 60C, start the tank at 40C and observe how long it takes to get the temperature up to 60C at 10,800kJ/hr.  Qdot*t=mcdT,   10,800*t = m*4.186*(60-40) input the mass of the water, and then solve for time, t.

Hope that helps,

Fred

Fred Betz  PhD., LEED AP
Sustainable Systems Analyst



AEI | AFFILIATED ENGINEERS, INC.
5802 Research Park Blvd. | Madison, WI  53719

P: 608.236.1175 | F: 608.238.2614
fbetz at aeieng.com<mailto:fbetz at aeieng.com>  |  www.aeieng.com<http://www.aeieng.com/>



From: Maurel Jeremy [mailto:Jeremy.Maurel at aldes.com]
Sent: Friday, May 07, 2010 4:23 AM
To: trnsys-users at cae.wisc.edu
Subject: [TRNSYS-users] storage tank and time step

hello trnsys user's

I wonder about type 60 (storage tank) and trnsys step time. The tank has a 10800 kJ/hour auxiliary heating and the trnsys time step is 0.05.
The problem is that when the heating is activated it delivers a power of 10800 kj/hour in 0.05 hour that is impossible. Do you know if this problem is solvable ?

Regards

[cid:image001.jpg at 01CAEDC2.F13BD8F0]
Maurel Jérémy
Stagiaire Ingénieur Recherche
Research Engineer Trainee
 www.aldes.com<http://www.aldes.com/>

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