# [TRNSYS-users] Questions about Type941 source code

Zhe Li zhe.li at dit.ie
Mon Apr 22 07:19:54 PDT 2013

```Dear David,

I am hoping you can clarify some of my confusions with this source
code(Type941). I have studied this Type941 source code carefully. From my
understanding is the outlet fluid temperature is not calculated from the
amount of heat contained in the air. The Capacity and Power is worked out
completely depending on the Rated Catalog Performance using the hourly
ambient temperature and temperature of the fluid. So why does the relative
humidity require at all? Is it only used to calculate the inlet and the
outlet air properties which is not going to affect the fluid temperature in
any way?

As I understand from previous questions, the interpolation Rated Catalog
Performance data could not be extrapolated from beyond the range provided?
However, what would be the calculation (selection) if the inlet ambient
temperature is 5oC and inlet water temperature is 27.5oC, how would the
fraction capacity and power calculated out (decided)?

Zhe Li

Sent: 19 April 2013 18:04
To: TRNSYS users mailing list at the Solar Energy Lab, UW-Madison
Cc: Zhe Li
Subject: Re: [TRNSYS-users] Question about a line in Type941 source code

Zhe,
lps_air is the volumetric flow rate of the air (in liters per second) and
rho_air_dry_in is the density (in kg/m3) of the dry air at the heat pump
inlet temperature.
Best,
David

On 4/19/2013 11:11, Zhe Li wrote:

Dear All,

I am trying to understand how TRNSYS calculates power output from this
air-water heat pumps (Type941).

I am stuck in a line which I don’t know what the two terms are standing for?

! Determine the dry air mass flow rate

Flow_air = lps_air*3.6*rho_air_dry_in

Could somebody let me know what are the lps_air and rho_air_dry_in standing
for?

I hope I did not break TRNSYS source code rule by asking this question.

Zhe Li

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