Cooling - Revision history

Michel Lamontagne: /* Mass transfer and phase change */

2024-04-16T15:15:45Z

Mass transfer and phase change

Michel Lamontagne: /* Conduction */

2024-04-11T16:01:31Z

Conduction

Michel Lamontagne at 15:58, 11 April 2024

2024-04-11T15:58:41Z

Michel Lamontagne: /* Convection */

2023-05-19T19:58:13Z

Convection

Michel Lamontagne: /* References */

2023-05-19T19:54:38Z

References

Michel Lamontagne: /* Convection */

2023-05-19T19:54:17Z

Convection

Michel Lamontagne at 19:34, 19 May 2023

2023-05-19T19:34:18Z

Michel Lamontagne: /* Conduction */

2023-05-19T19:29:12Z

Conduction

Michel Lamontagne: /* Mass transfer and phase change */

2023-05-19T19:22:12Z

Mass transfer and phase change

Michel Lamontagne: /* Convection */

2023-05-19T19:12:23Z

Convection

@@ Line 56: / Line 56: @@
 *dT is the temperature difference of the mass flow between the source and the heat sink (°K).
-A material can also either gain energy through phase change.  It can melt (solid to liquid), evaporate (liquid do gas) or sublimate (solid to gas) and gain energy, or it can lose energy by condensing (gas to liquid) or solidifying (liquid to solid).
+A material can also either gain or lose energy through phase change.  It can melt (solid to liquid), evaporate (liquid do gas) or sublimate (solid to gas) and gain energy, or it can lose energy by condensing (gas to liquid) or solidifying (liquid to solid).
 The phase change equation is '''Q=ṁ*Phe'''  where:
 Q = The phase change power (Watts)
@@ Line 62: / Line 62: @@
 *Phe is the phase change energy (J*/kg)
-Mass transfer usually requires compressors or pumps.  the equation for pump power is '''P=(Q*dp)/ɳ''' where:
+Mass transfer usually requires compressors (for gasses) or pumps (for liquids).  The equation for pump power is '''P=(Q*dp)/ɳ''' where:
 *P is the Pump power (Watts)

@@ Line 22: / Line 22: @@
 Challenges include the low temperature of the ground requiring a careful choice of working fluid, and interior humidity may deposit frost, and will certainly condensate, on cooling panels.
-Most regolith will have poor thermal conductivity, requiring either additional conduction area such as drilled cooling pipes or channels, or a soil treatment such as water injection to increase thermal conductivity by filling the soil pore voids with ice. The Insight mission has measured conductivity in the order of 0,04 W/m°K.  This is close to the thermal conductivity of polystyrene at 0,038 W/m°K.  So Martian regolith can be considered as an effective thermal insulator
+Most regolith will have poor thermal conductivity, requiring either additional conduction area such as drilled cooling pipes or channels, or a soil treatment such as water injection to increase thermal conductivity by filling the soil pore voids with ice. The Insight mission has measured conductivity in the order of 0,04 W/m°K.  This is close to the thermal conductivity of polystyrene at 0,038 W/m°K.  So Martian regolith can be considered as an effective thermal insulator.
 The conduction equation is: '''Q=U*A*dt''' or '''Q=k/t*A*dt''' where:
 *Q is the conduction heat transfer (Watts)
 *A is the area (m2)
 *U is the heat transfer coefficient (Watts/m2).  U=k/t where:
-*k is the thermal conductivity of a material in Watts/m*°K
+*k is the thermal conductivity of a material in Watts/m°K
 *t is the material thickness (m)

@@ Line 22: / Line 22: @@
 Challenges include the low temperature of the ground requiring a careful choice of working fluid, and interior humidity may deposit frost, and will certainly condensate, on cooling panels.
-most regolith will have poor thermal conductivity, requiring either additional conduction area such as drilled cooling pipes or channels, or a soil treatment such as water injection to increase thermal conductivity by filling the soil pore voids with ice.
+Most regolith will have poor thermal conductivity, requiring either additional conduction area such as drilled cooling pipes or channels, or a soil treatment such as water injection to increase thermal conductivity by filling the soil pore voids with ice. The Insight mission has measured conductivity in the order of 0,04 W/m°K.  This is close to the thermal conductivity of polystyrene at 0,038 W/m°K.  So Martian regolith can be considered as an effective thermal insulator
 The conduction equation is: '''Q=U*A*dt''' or '''Q=k/t*A*dt''' where:

@@ Line 11: / Line 11: @@
 *A is the area(m2)
 *h is the experimental coefficient for convective heat transfer (J/m2*°K)
-*dT is the temperature difference (°K) between the surface and the convecting fluid.
+*dT is the temperature difference (°K) between the surface and the convective fluid.
-A typical forced convection system on Mars for 100 kW of cooling might mass 300 kg, use a 4 kW fan and measure about 12m square(ref).
+A typical forced convection system on Mars for 100 kW of cooling might mass 300 kg, use a 4 kW fan and measure about 12m square(ref 3).
 ==Conduction==

@@ Line 69: / Line 69: @@
 [[Category: HVAC]]
 [[Category: Spacecraft design]]
 <references />

@@ Line 1: / Line 1: @@
-Because industrial, residential, or agricultural activities use energy, they will produce heat. Every human produces an average of 100 Watts of heat as well.  This heat eventually needs to be dissipated into the environment, or the [[temperature]] will rise and the settlement become too hot.  Heat can be transported via convection, conduction, and radiation, or by mass transfer and phase change.
+Because industrial, residential, or agricultural activities use energy, they will produce heat. Every human produces an average of 100 Watts of heat as well.  This heat eventually needs to be dissipated into the environment, or the [[temperature]] will rise and the settlement will become too hot.  Heat can be transported away from the settlement via convection, conduction, and radiation, or by mass transfer and phase change.
 Agriculture in particular requires large amounts of light, typically between 400 and 600 W/m2 to be productive.  This light turns into heat, that must be removed from the greenhouse or grow room.  A large part of the heat is transferred to water vapor by the plants by evapo-transpiration.  This water must be removed from the air by condensation (phase change) using cooling.   The cooling fluid removes the heat through mass transfer, and eventually heat transfer to the environment.
 ==Convection==
 <b>Convection</b> on Mars is minimal due to its very thin atmosphere, with even fan-assisted convection appearing to be less mass efficient than radiative cooling<ref>von Arx and Delgado, "Convective heat transfer on Mars", AIP Conference 1991    https://aip.scitation.org/doi/abs/10.1063/1.40133?journalCode=apc</ref>.

@@ Line 39: / Line 39: @@
 ==Mass transfer and phase change==
-The mass transfer equation is '''Q=ṁ*Cp*dT''' where Q is the power in Watts, ṁ is the mass flow in kg/s, Cp is the specific heat in Joules/kg/°K and dT is the temperature difference of the moving flow between the source and the heat sink.
+Heat can be transporter by moving a mass from one point, where it gains heat, to another, where it loses heat, through one or more of the heat transfer mechanisms mentioned above.
-The phase change equation is '''Q=ṁ*Phe'''  where m is the mass flow in kg/s and Phe is the phase change energy in J*/kg.  A fluid can either gain energy through phase change (melting, evaporation and sublimation) or lose energy (solidification, condensation).
+A material can also either gain energy through phase change.  It can melt (solid to liquid), evaporate (liquid do gas) or sublimate (solid to gas) and gain energy, or it can lose energy by condensing (gas to liquid) or solidifying (liquid to solid).
-Mass transfer usually requires compressors or pumps.  the equation for pump power is the following:
+Mass transfer usually requires compressors or pumps.  the equation for pump power is '''P=(Q*dp)/ɳ''' where:
-'''P=(Q*dp)/ɳ'''
+*P is the Pump power (Watts)
+*dp is the pressure change (Pa)
-P= Pump power (Watts)
+*Q is the Volume flow (m3/s)
+*ɳ is the pump efficiency  (usually between 0.6 and 0.8)
 ==References==

@@ Line 6: / Line 6: @@
 The convection equation is '''Q=h*A*dT''', where:
-*Q is the power (Watts)
+*Q is the convective heat transfer (Watts)
 *A is the area(m2)
 *h is the experimental coefficient for convective heat transfer (J/m2*°K)