Re: a qustion

[Michaël Kummert <kummert@xxxxxxxxxxxxx>]

Fardin,

> What’s different between algebraic tank (type38), stratified fluid 
> storage tank (type4) shapely?
>
> Which one is suitable to use for small water heating system please?
Type 4 and Type 38 are different models of the same component (a 
stratified fluid storage tank): Type 4 uses fixed nodes and calculates a 
mass and energy balance of each node at each time step. Type 38 uses the 
"plug-flow" method, i.e. using variable size segments of fluid (please 
refer to the TRNSYS manual for more details).

Type 38 can model horizontal and vertical cylindrical tanks, while Type 
4 is restricted to vertical cylindrical tanks. But Type 4 offers more 
options (2 different thermostats, variable insulation, 2 inlets and 2 
outlets at different heights, etc.)

Type 4 is usually the first model that users try to simulate a simple 
Domestic Hot Water System (solar or not). Its main limitation is that it 
uses a fixed time step (the TRNSYS time step) and fixed nodes, so it can 
become numerically unstable if you have high volume flowrates, 
especially if you use a large number of nodes (e.g. 10). The solution in 
that case is usually to decrease the timestep (e.g. from 1 hour to 25 
min) or to decrease the number of nodes (which reduces the maximum 
stratification that you can take into account).

Type 60 solves that problem by using its own time step. In addition, 
Type 60 allows you to simulate internal heat exchangers and it has two 
options for vertical and horizontal cylindrical tanks. Type 60 is 
usually the second model that users try when they want more than what 
Type 4 has to offer. It is a little more complex to configure than Type 
4, though. I must say that I do not have much experience using Type 38.

I hope this helps,

Michaël Kummert


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_________________________________________________________

Michaël Kummert

Solar Energy Laboratory - University of Wisconsin-Madison
1303 Engr Res Bldg, 1500 Engineering Drive
Madison, WI 53706

Tel: +1 (608) 263-1589
Fax: +1 (608) 262-8464
E-mail: kummert@engr.wisc.edu

SEL Web Site: http://sel.me.wisc.edu
TRNSYS Web Site: http://sel.me.wisc.edu/trnsys