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how to calculate the suction,discharge,and liquid line capacities
Hi, all
I am new and reading some books by myself, but something is difficult to understand, casually, I found this forum and people here are very kind.:)
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About the ASHRAE 2010(SI), chaper1 (halocarbon refrigeration systems), it gives some tables, but I don’t understand how the data calculated ou:confused:t:
1. Tables 3 and Table 4 both list suction line capacities under -40 and -30 SST, but why the corresponding Δp are different(marked in red), for example 196 in Table3 while 121 in Table 4 at SST=-40 ℃?
The pressure loss Δt=0.04k/m, I calculate the correspondingΔp, for example, =saturated pressure(@-40℃)- saturated pressure(@-40.04℃), right?
2. In the Table3, the discharge lines Δt=0.02k/m, but where does Δp=74.90 come from? And also liquid linesΔp=749?
3. How to calculate the capacities for suction, discharge, and liquid lines?
Best regards and thanks
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Re: how to calculate the suction,discharge,and liquid line capacities
Quote:
3. How to calculate the capacities for suction, discharge, and liquid lines?
About the suction line capacity, I think the calculation procedure maybe:
the capacity Q=cross section area of the pipe x velocity x density x unit capacity( enthalpy difference)
according the SST and refrigeration properties, we can get the density and the unit capacity.
About the velocity, because we know the corresponding pressure drop( Δt=0.04k/m), use the Darcy-Weisbach equation and Moody diagram to calculate out.
But the result I calculate is far away the table data.
So I reverse the calculation, use the capacity listed by the Table3 to get the velocity, and then use the Darcy-Weisbach equation to get the Reynolds number, friction factor.
But according to the MOODY diagram, the three parameters( Reynolds number, friction factor and relative roughness) don’t match to each other.
I don’t know what’s wrong with my calculation or maybe wrong from beginning?
I attach the calculating excel file.
I’m not native English speaker, excuse me my expression is not quite concise.
Any comments would be appreciate.
