Heat exchange apparatus

• US 4,222,436 A
• Filed: 12/21/1978
• Issued: 09/16/1980
• Est. Priority Date: 12/21/1978
• Status: Expired due to Term

• Current Assignee: Dynatherm Corp (Northrop Grumman Corporation)
• Original Assignee: Dynatherm Corp (Northrop Grumman Corporation)
• Inventors: Pravda, Milton F.
• Primary Examiner(s): Davis, Albert W.
• Application Number:
  US05/971,849
• Time in Patent Office: 635 Days
• Field of Search: 165/105, 165/DIG. 12
• US Class Current: 165/104.21
• CPC Class Codes: F24F 12/002 using an intermediate heat-transfer fluid
• CPC Class Codes: F28D 15/0266 with separate evaporating and condensing chambers connected by at least one conduit; Loop-type heat pipes; with multiple or common evaporating or condensing chambers F28D15/043 takes precedence
• CPC Class Codes: F28D 15/0275 Arrangements for coupling heat-pipes together or with other structures, e.g. with base blocks; Heat pipe cores
• CPC Class Codes: F28F 2200/005 Testing heat pipes
• CPC Class Codes: Y02B 30/56 Heat recovery units
• CPC Class Codes: Y10S 165/909 Regeneration
• CPC Class Codes: Y10T 29/49359 Cooling apparatus making, e.g., air conditioner, refrigerator

Abstract

Bidirectional heat exchangers and elements for use therein are provided for application in buildings and other enclosures to introduce fresh outside air and to remove exhaust air while coincidently recovering heat from the warmer air and using it to adjust the temperature of the cooler air.

Claims

1. In a bidirectional heat exchanger device for adjusting the air temperature in a first space by adding thereto air at a different temperature from a second space, wherein a first airway and a second airway are present for transferring air therethrough, means for keeping said airways separate, wherein working agent-containing heat exchange elements extend into and between said airways for transporting heat from the air in one airway to that in another, said elements each comprising an evaporator portion in one airway for receiving heat from heated air passing thereover and a condenser portion in the other airway for giving up heat to air passing thereover, and wherein said elements have a horizontal orientation which is difficult to establish and/or maintain and is subject to change during construction, installation, and/or operation of the device to produce unavoidable, accidental, and/or initially undetected adverse tilts, said adverse tilts being characterized by having said evaporator disposed above the level of the condenser and being of a magnitude as to reduce or even shut off the heat transport capability of the device,

the improvement wherein each element is a tube in the form of a closed, substantially horizontally disposed, evacuated, hermetically sealed loop comprising a pair of arms connected to each other at their ends by a pair of end members, one arm being disposed above the other such that a plane passing through longitudinal center lines of both arms makes an angle with the horizontal which is in the range of 15°

to 165°

, and said arms of each loop being spaced apart a distance of 1 to 25 arm diameters,

said working agent initially being disposed only in the lower of said arms of a loop and being present in the range of 34% to 51.3% of the loop internal volume,

said agent being vaporizable in the lower loop arms of the evaporator with resulting vapors flowing upwardly through adjacent end members of the evaporator to the upper arms and then along said upper arms to said condenser where they are condensed and the condensed agent then flowing down the end members adjacent thereto to the lower loop arms of the condenser and back to the evaporator, said agent in the form of vapor and condensate flowing cocurrently through said loops in the same direction,

each said loop having a liquid driving head for effecting heat transport which is in the range of 2.5 to 27 times the diameter of a loop arm and which is in the range of 2.5 to 27 times greater than the driving head of a conventional Perkins tube element, the diameters of the Perkins tube and the loop tube being the same,

said liquid driving head being reinforced by the action of the vapor flow which is cocurrent with the liquid flow, thereby to produce a combined driving head that is additionally greater than that of said Perkins tube which has a countercurrent vapor/liquid flow in which vapor shear reduces the liquid head by acting against the same,

each said loop in heat exchange operation being characterized by (1) transporting a substantially greater amount of thermal energy than a conventional Perkins tube under comparable conditions, by (2) transporting said greater amount of thermal energy, without burnout, at an adverse tilt of about 1 inch, thus exhibiting insensitivity to said tilt, whereas said Perkins tube under comparable conditions exhibits burnout at a substantially lower adverse tilt and at a substantially lower thermal energy transport level, and by (3) transporting more than twice the power, without burnout, than a conventional Perkins tube under comparable conditions,

said device being free of tilt-producing and/or tilt-changing mechanism while coincidently exhibiting an efficiency which is substantially insensitive to an adverse tilt of one inch and which is greater than 50% in the presence of an adverse tilt of 1 to 2 inches,

and said device, throughout bidirectional operation of the same, and by virtue of said insensitivity to adverse tilts, being rigidly attachable in place and to said airways, said attachment aiding the passive operational quality of the device.

2. Heat exchange device of claim 1 in which two agents are present in each loop, one having a lower boiling point than the other, in order to secure boiling at a lower temperature, thereby to reduce subcooling of liquid agent and to promote heat transfer by boiling over heat transfer by conduction.

3. Heat exchange device of claim 1 in which agent vapors may be present in the upper loop arm of the evaporator which are at a temperature above the critical temperature of the agent without rendering the device inoperative.