Heat Transfer Liquids:
Manufacturing Palm Oil
Palm Oil
Boiling Point: 300°C
Specific heat: 2.8kJ/(kg.°K)
Weight to Volume: 800Kg/m³
Heat Conductivity: 0.16W/(m.°K)
Heat Transfer Coefficient: 680W/(m²·°K)
Adding carbon nano tubes and causing a turbulent liquid flow can increase the Heat Transfer Coefficient.
Glycerol
Boiling Point: 290°C
Specific heat: 3.1kJ/(kg.°K) (This value does not vary a lot in the literature)
Weight to Volume: 1200Kg/m³
Heat Conductivity: 0.28W/(m.°K)
Heat Transfer Coefficient: 786W/(m²·°K).
Adding carbon nano tubes and causing a turbulent liquid flow can increase the heat transfer coefficient.
Thermal oils
Boiling Point: 300°C+
Specific heat: 2.8kJ/(kg.°K)
Heat Transfer Coefficient: 1kw/(m².°K) to 3.5kw/(m².°K)
Some of these oils already have nano particles in them.
Moving Heat from the Absorber Tube to the Heat Storage (HS)
Example Calculation Absorber Tube Heat Collecting Area to Liquid:
Heat Exchanger Methods
Tin - temperature in ºC
Tout - temperature out ºC
mf - mass flow rate: 1kg/s
Qss = mf * cp * Td
Td - Temp. Diff: (287ºC - 237ºC) = 50ºK
Qs - Amount of energy collected: kJ/s
U - Heat Transfer Coefficient W/m².°K
A - Heat Transfer Area From Absorber Tube: 2.64m² for 100kWh of solar concentrators.
Amount of heat collected per second.
Palm Oil
Qp = U * A * Td
Qp = 680W/(m²·°K) * 2.64m² * 50ºK = 89.760kW
Mass Flow rate/s
mp = Qp/(cp * Td)
mp = Qp/(2.8kJ/(kg.°K) * 50ºK) = 0.614kg/s
Glycerol
Qg = U * A * Td
Qg = 786W/(m²·°K) * 2.64m² * 50ºK = 103.75kW
Mass Flow rate/s
mg = Qg/(cp * Td)
mg = Qg/(3.1kJ/(kg.°K) * 50ºK) = 0.669kg/s
Therminol
Qt = U * A * Td
Qt = 3.5kw/(m².°K) * 2.64m² * 50ºK = 462kW
This liquid can be up to 4 times more expensive.
Mass Flow rate/s
mt = Qt/(cp * Td)
mt = Qt/(2.8kJ/(kg.°K)* 50ºK) = 3,3kg/s
The specific heat of Therminol that contains nano particles is not public.
Test Calculation, Palm Oil or Therminol:
For mf = 1kg/s
Q = mf * cp * Td
Qpt = 1kg * 2.8kJ/(kg.°K) * (50°K) = 140.4kJ
Test Calculation Glycerol:
For mf = 1kg/s
Q = mf * cp * Td
Qgl = 1kg * 3.1kJ/(kg.°K) * (50°K) = 155kJ
The values of Qp, Qg, Qpt and Qgl look all right, when using the characteristics of the heat conductors that have been made public.
If enough heat is on the absorber tube, increasing the mass flow rate of the Glycerol will also allow it to collect more heat.
That would mean adjusting the mass flow rate according to the temperature of the liquid on it's way back from the absorber tube.