Mhanley
Mechanical
- Nov 14, 2018
- 1
Hello I have been tasked with designing a heat exchanger for a heated platen press but have very limited knowledge of the subject. Here is what I have defined:
REQUIREMENTS:
CAN'T COOL FASTER THAN 5°F/MIN
MOLD TEMP AT COOLEST WILL BE 150°F IN BETWEEN CYCLES
CAN'T COOL SLOWER THAN 0.5°F/MIN
GIVEN:
Tdel = 160°F
TOTAL E OF SYSTEM = 60000BTU
(this comes from the mass of the platens, the Tdel, and specific heat capacity of steel)
m = mass
Q = Thermal Mass
⩝ = Volume
ρ = Density
ρsteel = ρ(steel) = 0.285lb/in³
ρair = ρ(air) = 0.075lb/ft³
ρ(fluid) = 6.33lb/gal
C = Specific heat capacity
Cpsteel = C(steel) = 0.122BTU/(lb °F)
Cpair = C(air) = 0.2403BTU/(lb °F)
Cp(fluid) = 0.6BTU/(lb°F)
The ambient temperatures of air and water are 70°F and 65°F respectively, water has a maximum flow rate of 6.5 Gal/min if we don't get a storage tank and a pump, these are the numbers of our ground water.
The water can be chilled if we buy a chiller in which case it would always come back to the primary Liquid to Liquid heat exchanger at an even cooler rate.
This system is a liquid to liquid heat exchanger with Paratherm NF fluid chosen as the primary fluid(as it won't boil until over 500°F) then to water and finally to air.
The system will rarely get below 150°F as that is the low point in it's cycle. 310°F is the high point of the cycle, it will cool from this to 150°F which we want to be able to control the rate.
There are 3 platens in contact with insulation boards on top and bottom, only exposed to convection from the sides. The coolant only flows through the middle platen which is about 430" in total length of the cooling lines at a 15/16" diameter.
I am having trouble calculating some of the flow rates; We were getting numbers of over 100 Gal/min which seems just crazy high for this application.
If there's something i'm missing that better defines the system I can put up any other information I have.
REQUIREMENTS:
CAN'T COOL FASTER THAN 5°F/MIN
MOLD TEMP AT COOLEST WILL BE 150°F IN BETWEEN CYCLES
CAN'T COOL SLOWER THAN 0.5°F/MIN
GIVEN:
Tdel = 160°F
TOTAL E OF SYSTEM = 60000BTU
(this comes from the mass of the platens, the Tdel, and specific heat capacity of steel)
m = mass
Q = Thermal Mass
⩝ = Volume
ρ = Density
ρsteel = ρ(steel) = 0.285lb/in³
ρair = ρ(air) = 0.075lb/ft³
ρ(fluid) = 6.33lb/gal
C = Specific heat capacity
Cpsteel = C(steel) = 0.122BTU/(lb °F)
Cpair = C(air) = 0.2403BTU/(lb °F)
Cp(fluid) = 0.6BTU/(lb°F)
The ambient temperatures of air and water are 70°F and 65°F respectively, water has a maximum flow rate of 6.5 Gal/min if we don't get a storage tank and a pump, these are the numbers of our ground water.
The water can be chilled if we buy a chiller in which case it would always come back to the primary Liquid to Liquid heat exchanger at an even cooler rate.
This system is a liquid to liquid heat exchanger with Paratherm NF fluid chosen as the primary fluid(as it won't boil until over 500°F) then to water and finally to air.
The system will rarely get below 150°F as that is the low point in it's cycle. 310°F is the high point of the cycle, it will cool from this to 150°F which we want to be able to control the rate.
There are 3 platens in contact with insulation boards on top and bottom, only exposed to convection from the sides. The coolant only flows through the middle platen which is about 430" in total length of the cooling lines at a 15/16" diameter.
I am having trouble calculating some of the flow rates; We were getting numbers of over 100 Gal/min which seems just crazy high for this application.
If there's something i'm missing that better defines the system I can put up any other information I have.