[TRNSYS-users] type 557a's question

Dear all,

I have several questions when I use type 557a to simulation ground heat exchanger in GSHP system.

1. I found that "the local heat transfer resistance from the fluid to the ground (or borehole thermal resistance) may depend on the flow condition, i.e.,it can be temperature and flow dependent" mentioned in some papers. I want to know how do I set parameters in type 557 to realize this function. And may you explain the calculating approach of borehole theraml resistance for you?

2. I check the source code of type 557, and found the following codes in line 525-528:
      OUT(9) =TUTMED(0)
      OUT(10)=TUTMED(1)
      DO 47 I=1,NRLOC-1
        IF (I.LE.10) OUT(10+I)=TUTMED(NRLOC+1-I)
   If I set the parameter 6 and 7 to 2, i.e., 2 boreholes are connected in series and the storage volume will be divided into 2 radial subregions, which temperature do OUT(9), OUT(10) and OUT(11) represent?

3. The DST model (refer to the paper writed by Pahud, D et al 1996) offer the possibility of having several ground layers that cross the storage region, and in source code of Type 557 also mentioned that "IF (PAR(9).LT.(-1.D-6)) THEN The thermal properties inside the storage volume may vary from layer to layer. They are set as those outside the storage volume". but when I set PAR(9) less than 0 (such as -1) and set PAR(39) numbers of ground layers to 3, furthermore set the thickness of layer-1 is 20m, the thickness of layer-2 is 30m and the thickness of layer-3 is 100 (I also set the PAR(2) Borehole depth to 100m), then I run the project and the error message "range check error" was appeared. I have no idea why.

I hopefully look forward to your answers.
Thank you in advance!

Dapeng Li