Abstract:
A testing apparatus measures cooling power of an electrically-powered Microclimate Cooling Unit (MCU) at the point of use of the MCU. The tester includes fluid supply and return ports for fluidly connecting to the MCU. A fluid heater provides a heat load to fluid in the tester. Fluid temperatures upstream and downstream of the heater are measured. The fluid flow rate is adjustable and measurable. A digital processor extracts the temperature and fluid flow rate data and computes cooling watts. The computed cooling watts are compared to the manufacturer&#39;s specifications to determine if the MCU is operating properly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of priority of U.S. provisional patent application Ser. No. 61/593,913 filed on Feb. 2, 2012, which is incorporated by reference herein. 
    
    
     STATEMENT OF GOVERNMENT INTEREST 
     The inventions described herein may be manufactured, used and licensed by or for the United States Government. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates in general to cooling systems and in particular to apparatus and methods for evaluating the performance of cooling systems. 
     Cooling systems help prevent heat stress in humans exposed to extreme climates or work environments. A personal cooling system enables chilled fluid to circulate through tubing placed in garments worn by a person. In some personal cooling systems, the tubing on the person is tethered or connected to heavier components (for example, heat exchangers) that cool the fluid in the tubing. Thus, the heavier components, including power supplies and compressors, are not carried by the person being cooled. Vehicle-mounted personal cooling systems may be mounted in a vehicle, such as an air or ground vehicle, and connected to a person or persons in the vehicle via the fluid tubing. A Microclimate Cooling Unit (MCU) mounted in a vehicle may be used to chill fluid that provides cooling to a vehicle&#39;s crew via tubing in garments worn by the crew. 
     The performance of an MCU can degrade because of normal wear and tear, physical damage, or excessive use. A performance-degraded MCU uses more power and cools less than an MCU that is operating at standard or normal efficiency. In some environments, loss of cooling results causes only personal discomfort. However, in very high temperature environments, such as compartments of armored vehicles deployed in a desert and containing many heat-producing electronic devices, the loss of cooling in the compartment can result in severe heat sickness. Heat sickness adversely affects humans&#39; decision-making abilities, which are critical to survival when engaged with hostile parties or when operating an air or land vehicle. 
     There exists no simple way to accurately test the performance of an MCU at its point of use. MCUs may be as small as about 6 inches by 6 inches by 14 inches with little space in the interior to access any of the refrigeration components for testing purposes. Also, the MCU housings are not easily opened at the point of use. 
     An MCU can be shipped from its point of use to another location, such as the manufacturer&#39;s facility, for testing with a laboratory testing system. The heat load used to test an MCU in a laboratory test system is generally a multi-gallon capacity heated water reservoir. The manufacturer&#39;s testing system is accurate, although it is not portable. The size and weight of the water reservoir and the power need to heat the water in the reservoir preclude ease of portability. So, the MCU must be shipped from its point of use to the laboratory testing system. This process is expensive and time-consuming because all MCUs, whether performance-degraded or not, must be sent to the manufacturer for testing. 
     An onsite temperature differential test can be used to provide some indication of MCU performance. The temperature differential test includes measuring surface temperature at two locations on a bottom surface of the MCU, using a hand-held infrared temperature sensor. If the difference in temperature between the two locations is greater than 10 degrees F., then the MCU is considered to be performing adequately. While better than no test at all, the temperature differential test does not provide a very accurate indication of the actual cooling performance of an MCU. No heat load is applied to the MCU using the temperature differential test. Thus, properly-performing MCUs may be misdiagnosed as performance-degraded and shipped away for further testing, and performance-degraded MCUs may be misdiagnosed as properly-performing and not shipped for further testing. 
     In the case of the U.S. Army, over 7,000 MCUs have been deployed in Army aviation and ground vehicles. It is costly and time-consuming to ship this large number of MCUs from their respective points of use to suitable locations for performance testing. A need exists for a more accurate performance testing apparatus that can be used at the point of use of an MCU. 
     SUMMARY OF INVENTION 
     One aspect of the invention is an apparatus for measuring cooling power of an electrically-powered Microclimate Cooling Unit (MCU) at a point of use of the MCU. The apparatus includes a fluid supply port connected to a fluid conduit and a flow rate controller disposed in the fluid conduit. The flow rate controller includes an analog flow meter. A fluid heater heats fluid in the fluid conduit downstream of the fluid supply port. A first thermocouple measures supply fluid temperature in the fluid conduit downstream of the fluid supply port and upstream of the fluid heater. A digital flow meter is disposed in the fluid conduit. A fluid return port is connected to the fluid conduit downstream of the fluid heater. A second thermocouple measures return fluid temperature in the fluid conduit downstream of the fluid heater and upstream of the fluid return port. 
     A power supply is connected to the fluid heater via a relay. At least one cooling fan is connected to the power supply. A housing contains the fluid conduit, the flow rate controller, the first and second thermocouples, the fluid heater, the relay, the digital flow meter, the power supply and the at least one cooling fan. The housing includes an exterior. The exterior has mounted thereon: a) visual displays of the supply temperature measured by the first thermocouple, the return temperature measured by the second thermocouple, and flow rates measured by the digital flow meter; b) a return temperature controller that is connected to the relay; c) the flow rate controller and analog flow meter; d) the fluid supply port and the fluid return port; e) power switches for the fluid heater, the apparatus for measuring cooling power, and the MCU; f) a power supply connection for the MCU; g) a control cable connection for the MCU; and h) a controller for the MCU. 
     A computer extracts the temperatures measured by the first and the second thermocouples and the flow rates measured by the digital flow meter and computes cooling power in real-time. In one embodiment, the computer is disposed inside the housing and the apparatus includes a visual display of the cooling power, located on the exterior of the housing. 
     In another embodiment, the computer is disposed external to the housing and the apparatus includes a data acquisition hub on the exterior of the housing. The data acquisition hub and the computer may be connected by a cable. The computer extracts real-time values of the temperatures measured by the first and second thermocouples and flow rates measured by the digital flow meter. 
     Another aspect of the invention is a method that includes providing an apparatus for measuring cooling power of an electrically-powered Microclimate Cooling Unit (MCU). The MCU is mounted in a vehicle and the point of use of the MCU is in the vehicle. The method includes measuring cooling power of the MCU at the MCU point of use. 
     The invention will be better understood, and further objects, features and advantages of the invention will become more apparent from the following description, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, which are not necessarily to scale, like or corresponding parts are denoted by like or corresponding reference numerals. 
         FIG. 1  is a schematic drawing of an MCU and an MCU tester. 
         FIG. 2  is a schematic drawing of one embodiment of an MCU tester. 
         FIG. 3  is a schematic drawing of an exterior of a housing for an MCU tester. 
         FIG. 4  is a schematic drawing of a computer. 
         FIG. 5  is a schematic drawing of a microprocessor. 
         FIG. 6A  is a schematic drawing of a ground vehicle with an MCU mounted therein. 
         FIG. 6B  is a schematic drawing of an air vehicle with an MCU mounted therein. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic drawing of one embodiment of an electrically-powered Microclimate Cooling Unit (MCU)  10  and one embodiment of an MCU cooling performance testing apparatus or tester  12 . Suitable MCUs  10  are available from, for example, Cobham Life Support, 10 Cobham Drive, Orchard Park, N.Y., USA, 14127. 
     MCU  10  is typically mounted in a vehicle, such as an air or ground vehicle.  FIG. 6A  is a schematic drawing of a ground vehicle  76  with an MCU  10  mounted therein.  FIG. 6B  is a schematic drawing of an air vehicle  78  with an MCU  10  mounted therein. Tester  12  is used to determine the cooling power of MCU  10 . For testing purposes, tester  12  is connected to MCU  10  via a fluid supply connection  14 , a fluid return connection  15 , an electrical power cable  16 , and a control cable  18 . Importantly, tester  12  is able to test MCU  10  at the point of use of the MCU  10 . 
     Fluid cooled by MCU  10  is supplied to tester  12  via fluid supply connection  14 . Fluid heated by tester  12  is returned to MCU  10  via fluid return connection  15 . Fluid connections  14  and  15  may be, for example, insulated hoses. A fluid reservoir (not shown) with a capacity on the order of a pint may be interposed between MCU  10  and tester  12  in either the fluid supply connection  14  or the fluid return connection  15  as a means to purge air from the fluid system. The method of using such a reservoir to purge air is known. Tester  12  supplies power to MCU  10  via power cable  16 . Tester  12  controls the cooling output of MCU  10  via control cable  18 . 
       FIG. 2  is a schematic drawing of one embodiment of MCU tester  12 . Tester  12  includes a fluid supply port  20  connected to a fluid conduit  22 . A flow rate controller  24  and an analog flow meter  26  are disposed downstream of fluid supply port  20 . A fluid heater  30  heats fluid in fluid conduit  22  downstream of fluid supply port  20 . A thermocouple  28  measures fluid temperature in fluid conduit  22  downstream of fluid supply port  20  and upstream of fluid heater  30 . A power supply  38  supplies power to fluid heater  30  via a relay  39 . At least one cooling fan  40  is powered by power supply  38 . A digital flow meter  32  is disposed in fluid conduit  22 . A fluid return port  34  is connected to fluid conduit  22  downstream of fluid heater  30 . A thermocouple  36  measures fluid temperature in fluid conduit  22  downstream of fluid heater  30  and upstream of fluid return port  34 . 
     A housing  42  contains fluid conduit  22 , flow rate controller  24 , thermocouples  28  and  36 , fluid heater  30 , digital flow meter  32 , power supply  38 , and cooling fan  40 . Preferably, two fans  40  may be used, an intake fan and an exhaust fan. Housing  42  may be made of a metal and may include a removable lid for easy access to the interior of housing  42 . Housing  42  includes an exterior  44  ( FIG. 3 ). Exterior  44  may include front and side panels. For ease of use, exterior  44  includes fluid and electrical connections for connecting tester  12  to MCU  10 . A variety of visual displays and controls are also located on exterior  44 . Preferably, the connections, visual displays and controls are located on a front panel of exterior  44 . 
     Referring to  FIG. 3 , exterior  44  has mounted thereon a visual display  46  of the supply temperature measured by thermocouple  28 , a visual display  48  of the return temperature measured by thermocouple  36 , a visual display  50  for analog flow meter  26 , and a visual display  52  for digital flow meter  32 . Fluid supply port  20  and fluid return port  34  are mounted on exterior  44 . Controls on exterior  44  include flow rate controller  24 , a power switch  56  for fluid heater  30 , a power switch  58  for tester  12 , a power switch  60  for MCU  10 , and a controller  66  for controlling the cooling output of MCU  10 . Electrical connections on exterior  44  include a control cable connection  64  for connecting control cable  18  to MCU  10  and a power supply connection  62  for connecting power cable  16  to MCU  10 . A data output port  68  on exterior  44  enables temperature and flow data to be extracted from tester  12 . Visual displays  46 ,  48 , and  52  may be, for example, liquid crystal displays. 
     Supply fluid connection  14  ( FIG. 1 ), such as a hose, is connected between fluid supply port  20  on tester  12  and a fluid supply port  120  on MCU  10 . Return fluid connection  15  ( FIG. 1 ), such as a hose, is connected between fluid return port  34  on tester  12  and a return port  134  on MCU  10 . Control cable  18  ( FIG. 1 ), such as a wiring harness, is connected between control cable connector  64  on tester  12  and a control connector  164  on MCU  10 . Control signals from controller  66  on tester  12  are sent via control cable  18  to MCU  10  to vary the cooling output of MCU  10 . Electric power cable  16  ( FIG. 1 ), such as a wiring harness, is connected between power supply connector  62  on tester  12  and a power connector  162  on MCU  10 . Connector  62  is also connected to power supply  38 . Tester  12  supplies power to MCU  10  during performance testing of MCU  10 . 
     Flow rate controller  24  may include a knob to adjust the flow in fluid conduit  22 . Some performance testing may require a specific flow rate in conduit  22 . The flow rate may be viewed on analog flow meter display  50 . Controller  66 , for example, a knob, controls the cooling output of MCU  10  via control cable  18 . Data output port  68 , such as a USB connection or USB data acquisition hub, enables digital output of real-time values of the temperatures measured by thermocouples  28  and  36  and the flow rate measured by digital flow meter  32 . 
     In one embodiment, a portable computer  70  ( FIG. 4 ), for example, a notebook or laptop computer, may be connected via cable  71  to data output port  68  to extract and record the temperature and flow rate values. Computer  70  may calculate the cooling power of MCU  10  using known algorithms. The known algorithms calculate cooling power (watts) from the temperatures measured by thermocouples  28  and  36  and the flow rate measured by digital flow meter  32 . The calculated cooling power is then compared to the manufacturer&#39;s specifications to determine if the MCU  10  is cooling properly. 
     In another embodiment, tester  12  may include an internal computer such as a microprocessor  72  ( FIG. 5 ) disposed inside of housing  42 . Microprocessor  72  may extract and record the temperature and flow rate values, perform the cooling power calculations, and display the calculated cooling watts visually on a display  74  on exterior  44 . Microprocessor  72  may include memory to store the temperature, flow rate, and cooling watts data. Data output port  68  may be used to access the information in the memory. Computer  70  may not be needed if microprocessor  72  is used. 
     To test the cooling performance of MCU  10 , power supply  38  of tester  12  is connected to an external power supply, for example, a 115 volt AC power outlet. Fluid return port  34  of tester  12  is connected via return connection (hose)  15  to return port  134  on MCU  10 . Supply connection (hose)  14  is connected to supply port  120  on MCU  10  and to fluid supply port  20  on tester  12 . Preferably, a small fluid reservoir (not shown) is interposed in a known manner in return or supply fluid connection  15  or  14  to allow air to escape from the fluid system. 
     Control cable or harness  18  is connected to control connection  64  on tester  12  and to control connection  164  on MCU  10 . Power cable  16  is connected between power connection  62  on tester  12  and power connection  162  on MCU  10 . Computer  70  (if used) is connected to data output port  68 . Main power switch  58  is moved to the on position and then MCU power switch  62  is moved to the on position. MCU controller  66  is moved to the maximum cooling position. The fluid in fluid conduit  22  is cooled by MCU  10  until the supply temperature measured by thermocouple  28  is the same as the return temperature measured by thermocouple  36 . This may take about 30 seconds. 
     Next, power to heater  30  is enabled using power switch  56 . Incorporated with or separate from return temperature display  48  is a return temperature control  54  for setting a desired return temperature at thermocouple  36 . Control  54  is connected to a relay  39  that is connected to power supply  38 . Relay  39  enables power to heater  30  as needed. Use of relay  39  enables the use of a smaller and less massive power supply  38 . Power to heater  30  may be, for example, 110 volt AC power. The fluid temperature in fluid conduit  22  will increase until the return temperature at thermocouple  36  is the temperature set by temperature control  54 . In some embodiments, the set temperature is about 80 degrees F. 
     Once the supply temperature at thermocouple  28  is stable, the temperatures at thermocouples  28  and  36  and the flow rate at digital flow meter  32  may be used to calculate the cooling power of MCU  10 . The cooling power of MCU  10  may be calculated by external computer  70  or internal microprocessor  72 . The calculated cooling power is then compared to the manufacturer&#39;s specifications to determine if the MTU  10  should be shipped from the point of use for repair or replacement. 
     Preferably, tester  12  weighs less than fifty pounds. More preferably, tester  12  weighs no more than thirty-one pounds. As defined by the U.S. Dept. of Defense, a “man portable” device weighs no more than thirty-one pounds. The man portable embodiment uses microprocessor  72  disposed in the interior of housing  42 . 
     While the invention has been described with reference to certain embodiments, numerous changes, alterations and modifications to the described embodiments are possible without departing from the spirit and scope of the invention as defined in the appended claims, and equivalents thereof.