Evaporative cooling membrane device

• US 5,946,931 A
• Filed: 02/25/1998
• Issued: 09/07/1999
• Est. Priority Date: 02/25/1998
• Status: Expired due to Fees

• Current Assignee: Administrator of The National Aeronautics and Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Lomax, Curtis, Moskito, John
• Primary Examiner(s): Bennett, Henry
• Application Number:
  US09/030,101
• Time in Patent Office: 559 Days
• Field of Search: 62/304, 62/309, 62/315, 261/101, 261/100, 261/DIG. 3
• US Class Current: 62/304
• CPC Class Codes: B64G 1/50 for temperature control
• CPC Class Codes: B64G 1/58 Thermal protection, e.g. heat shields
• CPC Class Codes: B64G 6/00 Space suits
• CPC Class Codes: F24F 2003/1435 comprising semi-permeable membrane
• CPC Class Codes: F24F 5/0035 using evaporation
• CPC Class Codes: F28D 5/00 Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, using the cooling effect of natural or forced evaporation
• CPC Class Codes: Y02B 30/54 Free-cooling systems
• CPC Class Codes: Y10S 261/03 Air cooling

Abstract

An evaporative cooling membrane device is disclosed having a flat or pleated plate housing with an enclosed bottom and an exposed top that is covered with at least one sheet of hydrophobic porous material having a thin thickness so as to serve as a membrane. The hydrophobic porous material has pores with predetermined dimensions so as to resist any fluid in its liquid state from passing therethrough but to allow passage of the fluid in its vapor state, thereby, causing the evaporation of the fluid and the cooling of the remaining fluid. The fluid has a predetermined flow rate. The evaporative cooling membrane device has a channel which is sized in cooperation with the predetermined flow rate of the fluid so as to produce laminar flow therein. The evaporative cooling membrane device provides for the convenient control of the evaporation rates of the circulating fluid by adjusting the flow rates of the laminar flowing fluid.

Claims

1. A system for cooling a contained environment with a circulating stream of fluid by means of vaporation comprising:

a) a housing with four enclosed side walls, an enclosed bottom, and an exposed face covered with at least one sheet of hydrophobic porous material of teflon of the PTFE type, said side walls including two oppositely disposed side walls one with an entrance opening and the other with an exit opening and with entrance opening capable of receiving a fluid having an elevated temperature and a predetermined flow rate and capable of experiencing a liquid to a vapor change and the exit opening capable of passing said fluid out of said housing, said predetermined flow being selected so that laminar flow is maintained from said entrance opening to said exit opening, said porous material having pores with predetermined dimensions so as to resist any fluid in its liquid state from passing therethrough but to provide passage of said fluid in its vapor state causing the evaporation of said fluid;

b) a container defining said confined environment and capable of containing a negative pressure, said container having means for holding said housing so that said porous material is exposed to said negative pressure.

3. The system for cooling according to claim 1, wherein said predetermined dimensions of said pores comprise a diameter in the range from 0.1 μ

m to 0.5 μ

m.

6. The system according to claim 1, wherein the vapor state of said fluid passing through and evaporating from said pores creates a combination of heat and mass transfer around and through said housing to provide four definable processes which are:

(1) transfer of heat to the site of each of said pores of said evaporation;

(2) the permeation of mass to the site of each of said pores of said evaporation;

(3) the evaporation of mass from the site of each pore of said evaporation; and

(4) the flow of vapor from the site of each pore of said evaporation.

2. A system for cooling with a circulating stream of fluid by means of evaporation comprising:

a housing with four enclosed side walls, an enclosed bottom, and an exposed face covered with at least one sheet of hydrophobic porous material of teflon of the PTFE type, said side walls including two oppositely disposed side walls one with an entrance opening and the other with an exit opening and with entrance opening capable of receiving a fluid having an elevated temperature and a predetermined flow rate and capable of experiencing a liquid to a vapor change and the exit opening capable of passing said fluid out of said housing, said predetermined flow being selected so that laminar flow is maintained from said entrance opening to said exit opening, said porous material having pores with, predetermined dimensions so as to resist said fluid in its liquid state from passing therethrough but to allow passage of said fluid in its vapor state causing the evaporation of said fluid;

said pores material having inner and outer surfaces with the outer surface being arranged to be exposed to a negative pressure.

4. The system for cooling according to claim 2, wherein said predetermined dimensions of said pores comprise a diameter in the range from 0.1 μ

m to 0.5 μ

m.

5. The system according to claim 2, wherein said hydrophobic material has a selected thickness so as to comprise a membrane.

7. The system according to claim 2, wherein the vapor state of said fluid passing through and evaporating from said pores creates a combination of heat and mass transfer around and through said housing to provide four definable processes which are:

(1) transfer of heat to the site of each of said pores of said evaporation;

(2) the permeation of mass to the site of each of said pores of said evaporation;

(3) the evaporation of mass from the site of each pore of said evaporation; and

(4) thus flow of vapor from the site of each pore of said evaporation.