Cooling - Revision history

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

2024-04-16T15:15:45Z

Mass transfer and phase change

← Older revision		Revision as of 16:15, 16 April 2024
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	*dT is the temperature difference of the mass flow between the source and the heat sink (°K).		*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:		The phase change equation is '''Q=ṁ*Phe''' where:
	Q = The phase change power (Watts)		Q = The phase change power (Watts)
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	Phe is the phase change energy (J/kg)		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)		*P is the Pump power (Watts)

Michel Lamontagne: /* Conduction */

2024-04-11T16:01:31Z

Conduction

← Older revision		Revision as of 17:01, 11 April 2024
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	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.		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=UAdt''' or '''Q=k/tAdt''' where:		The conduction equation is: '''Q=UAdt''' or '''Q=k/tAdt''' where:
	*Q is the conduction heat transfer (Watts)		*Q is the conduction heat transfer (Watts)
	*A is the area (m2)		*A is the area (m2)
			*dt is the temperature difference
	*U is the heat transfer coefficient (Watts/m2). U=k/t where:		*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)		*t is the material thickness (m)

Michel Lamontagne at 15:58, 11 April 2024

2024-04-11T15:58:41Z

← Older revision		Revision as of 16:58, 11 April 2024
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	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.		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=UAdt''' or '''Q=k/tAdt''' where:		The conduction equation is: '''Q=UAdt''' or '''Q=k/tAdt''' where:

Michel Lamontagne: /* Convection */

2023-05-19T19:58:13Z

Convection

← Older revision		Revision as of 20:58, 19 May 2023
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	*A is the area(m2)		*A is the area(m2)
	h is the experimental coefficient for convective heat transfer (J/m2°K)		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).

			The temperatures of the coolant (CO2) would vary from 400 to 350 °K, for an environment at 260 K. This might be used to cool a nuclear reactor, or a Sterling engine using a Brayton cycle.

	==Conduction==		==Conduction==

Michel Lamontagne: /* References */

2023-05-19T19:54:38Z

References

← Older revision		Revision as of 20:54, 19 May 2023
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	[[Category: HVAC]]		[[Category: HVAC]]
	[[Category: Spacecraft design]]		[[Category: Spacecraft design]]

	<references />		<references />

			3- Colgan, N., Nellis, G., & Anderson, M. (2021). Forced Convection Heat Rejection System for Mars Surface Applications. In Proceedings of the Wisconsin Space Conference (Vol. 1, No. 1).

Michel Lamontagne: /* Convection */

2023-05-19T19:54:17Z

Convection

← Older revision		Revision as of 20:54, 19 May 2023
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	h is the experimental coefficient for convective heat transfer (J/m2°K)		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 convecting 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).

	==Conduction==		==Conduction==

Michel Lamontagne at 19:34, 19 May 2023

2023-05-19T19:34:18Z

← Older revision		Revision as of 20:34, 19 May 2023
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	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.		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.
			When designing a Martian settlement, a heat balance must be established between the heat gains from the processes in the settlement and solar loads during the day, and the losses to the environment.

	==Convection==		==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>.		<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>.

Michel Lamontagne: /* Conduction */

2023-05-19T19:29:12Z

Conduction

← Older revision		Revision as of 20:29, 19 May 2023
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	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.		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.

	~~Some~~ regolith~~, such as dry dust or loose rock, may~~ 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.
	~~Then~~ conduction equation is: '''Q=UAdt''' or '''Q=k/tAdt''' where:
			The conduction equation is: '''Q=UAdt''' or '''Q=k/tAdt''' where:
	*Q is the conduction heat transfer (Watts)		*Q is the conduction heat transfer (Watts)
	*A is the area (m2)		*A is the area (m2)
	*U is the heat transfer coefficient		*U is the heat transfer coefficient (Watts/m2). U=k/t where:
			k is the thermal conductivity of a material in Watts/m°K
			*t is the material thickness (m)

	==Radiation==		==Radiation==

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

2023-05-19T19:22:12Z

Mass transfer and phase change

← Older revision		Revision as of 20:22, 19 May 2023
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	==Mass transfer and phase change==		==Mass transfer and phase change==
	The mass transfer equation is '''Q=ṁCpdT''' 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 mass transfer equation is '''Q=ṁCpdT''' where:
			*Q is the power (Watts)
			*ṁ is the mass flow (kg/s)
			*Cp is the specific heat (Joules/kg/°K). The amount of heat a given material can store. Water, for example, store 4,18 kJ/kg/°K.
			*dT is the temperature difference of the mass flow between the source and the heat sink (°K).

	The phase change equation is '''Q=ṁPhe''' 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).
			The phase change equation is '''Q=ṁ*Phe''' where:
			Q = The phase change power (Watts)
			*m is the mass flow (kg/s)
			Phe is the phase change energy (J/kg)

	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)
	dp=pressure change (Pa)

	Q=Volume flow (m3/s)

	ɳ=pump efficiency (usually between 0.6 and 0.8)

	==References==		==References==

Michel Lamontagne: /* Convection */

2023-05-19T19:12:23Z

Convection

← Older revision		Revision as of 20:12, 19 May 2023
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	The convection equation is '''Q=hAdT''', where:		The convection equation is '''Q=hAdT''', where:
	*Q is the ~~power~~ (Watts)		*Q is the convective heat transfer (Watts)
	*A is the area(m2)		*A is the area(m2)
	h is the experimental coefficient for convective heat transfer (J/m2°K)		h is the experimental coefficient for convective heat transfer (J/m2°K)