RE: [EnergyPlus_Support] Solar collector example file

["Ellis, Peter" <peter_ellis@xxxxxxxx>]

Hi Andrea,
 
The "Water Heater Source Outlet Node" and "Collector Loop Inlet Node" are technically different nodes, one on the source side of the loop and the other on the demand side of the loop.  The two nodes, however, are directly connected by the interface between the two sides of the loop, so it's natural to expect that they should have the same temperature at all times.  The reason that they do not have the same temperature is because it is necessary to simulate the loop with some thermal capacitance in order to achieve stability of the solution.  In a real system, this thermal capacitance is the mass of the water in the pipes.  This can be input using the "volume of the plant loop" field in the PLANT LOOP object, but most times we autosize that number, which calculates the minimum volume necessary for a stable solution.  The jump from "source loop side outlet node" to "demand loop side inlet node" is where we calculate the effects of the thermal capacitance, which results in a tem
 perature difference.  If you look closely at any plant loop, you'll see that there is always a temperature difference between the "source loop side outlet node" and the "demand loop side inlet node".  
 
Peter Ellis
National Renewable Energy Laboratory
 

	-----Original Message----- 
	From: ingdallolio [mailto:ing.dallolio@xxxxxxxxx] 
	Sent: Mon 1/24/2005 8:38 AM 
	To: EnergyPlus_Support@xxxxxxxxxxxxxxx 
	Cc: 
	Subject: [EnergyPlus_Support] Solar collector example file
	
	
	
	All,
	I'm looking to the solar collector example file (that comes with E+), 
	in the output file I get, the WATER HEATER SOURCE OUTLET NODE:System 
	Node Temp[C](TimeStep) ( column H in the speadsheet )  is not the 
	same as the COLLECTOR LOOP INLET NODE:System Node Temp[C](TimeStep)( 
	column J in the spreadsheet), does that make sense ? are they not the 
	same node ?
	Thanks a lot for reading this.
	Andrea.  
	
	
	
	
	
	
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