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The NAVAIRDEVCEN (Naval Air Development Center) is developing a personal cooling system for helicopter pilots to alleviate the heat stress encountered during exposure to high ambient temperatures. The major components of this system are a lightweight, constant-wear, liquid circulating garment (LCG) outfitted with skin temperature sensors, a cooling generator, and an automatic controller. The liquid circulation garment is designed for wear under a standard flight coverall and is connected, upon aircraft entry, to the generator and automatic controller. During flight, the system automatically maintains the pilot and copilot in thermal comfort thereby enabling more effective performance of flight duties. The system is currently under a development contract. (Author)

The specific objectives of Phase I of this program (covering the period of 10-76 to 4-78) are (1) to design and develop a reliable beam optical system, focusing mechanism and suitable collector for a high power, high perveance, broadband TWT, (2) to deliver one beam tester suitable for design evaluation and initial systems modulator testing, and (3) to carry out sufficient cold test measurements to design a suitable output coupler with fluid adapter, rf structure, and cooling mechanism for use in the engineering models to be built in Phase II. (Author)

An experimental test facility capable of investigating plain and enhanced horizontal tubes was built. The test facility consists of an electric boiler, test condenser and associated piping for steam, condensate and cooling water. Performance of the test condenser was checked at a steam pressure of 3 psia with cooling water velocities ranging from 5 to 25 ft/sec. Condensation data was obtained for a single, 0.625 inch outside diameter, 90-10 copper-nickel tube in a simualted tube bundle to determine the overall, inside and outside heat transfer coefficients. The overall heat transfer coefficient was determined directly from experimental data, and the Wilson Plot technique was used to determine the inside and outside heat transfer coefficients. The experimentally obtained values for the inside heat transfer coefficient are within 5 percent of the theoretical values predicted by the Sieder-Tate equation. The experimental values obtained for the outside heat transfer coefficient are within 8 percent of the theoretical values predicted by the Nusselt equation. (Author)

An analytical model has been developed for two problems of gun-barrel cooling: (a) film cooling with wear reducing additives and (b) liquid film cooling. The governing equations were derived from an integral method and the solutions of the film-cooling effectiveness were obtained by application of the characteristic method. The results found earlier are: (a) with the additives, the effectiveness is very significant in a region where the erosion is most series and (b) with liquid cooling, the effectiveness is in general high. It is, however, smaller in that region. (Author)

Dielectric coolant fluids operating in an evaporation-condensation cooling cycle were investigated to determine how much they could reduce the surface temperature of high power density semiconductor devices. A brief description of the process reveals that the air-side thermal resistance of the condenser and the critical heat flux density of the fluid at the semiconductor surface are problem areas. Ther thermal resistance and time constant of several TRAPATT diodes and microwave transistors were measured. The heat flux density at the surface of the TRAPATT diodes was too high to be compatible with conventional fluids. The junction temperature of microwave transistors was consistently reduced 10 C, and the process has a potential application in this area. (Author)

In the conventional helix traveling wave tube the helix is supported by three or four ceramic rods between the helix and tube shell. The amount of average power attainable is limited by the amount of heat that can be conducted along the helix and across the ceramic supports. A fluid-cooled helix was designated that employs a helix made of copper tubing supported by hollow ceramic tubing brazed at each half turn of the helix. Several geometries of fluid flow and their effect on the RF design of the tube were tested. The cooling analyses indicate that it should be possible to dissipate at least five times as much power with the fluid cooling as with conventional thermal conduction for frequencies up through S-band. For some fluids the circuit RF losses increase rapidly with frequency above the operating frequency. This is useful for suppressing unwanted backward-wave oscillations. Experimental tubes were built and tested. Four kilowatts of average power was attained at 3 GHz in a design that was capable of octave bandwidth operation.

The Engineering Design Handbook Series of the US Army Materiel Command is a coordinated series of handbooks containing basic information and fundamental data useful in the design and development of Army materiel and systems. The handbooks are authoritative reference books of practical information and quantitative facts presented to be helpful in the design and development of materiel that will meet the technical needs of the Armed Forces. The Military Vehicle Power Plant Cooling Handbook is intended to serve as a basic reference for the vehicle cooling system designer. The material presented was compiled from reports, publications, interviews, and data provided by various agencies. This handbook will be of particular value to the users and program managers in their role in the development of new vehicles. It will serve as a guide to (a) the generation of realistic vehicle specifications, (b) total system integration in cooling system design, and (c) a complete cooling system development and corrective action program in the vehicle development cycle.

The Navy Clothing & Textile Research Facility (NCTRF), under contract to the Navy Science Assistance Program(NSAP), evaluated the feasibility of using commercial microclimate cooling systems (MCS) in the high heat areas onboard Navy ships by conducting an evaluation aboard the USS LEXINGTON (AVT16) from 30 March to 9 April 1987. The following cooling systems were evaluated: three liquid-cooled MCS - the LSSI Cool Head, the LSSI Portapack, and the ILC Cool Vest; and two air-cooled MCS - the Encon Air System, with and without a vortex tube. Both air systems and the LSSI Portapack MCS were tethered. The remaining two MCS's were portable, battery-operated, backpack systems. A control test with no cooling system was also run. The evaluation consisted of having test subjects wear the MCS during their normal duty and collecting physiological, subjective, and logistical data. During the test period, environmental conditions were relatively mild: the Wet Bulb Globe Temperature (WBGT) did not rise above 34C, and the average WBGT was 24C. Keywords: Microclimate cooling systems; Shipboard testing of microclimate cooling systems; Physiological testing; Heat stress; Commercial microclimate cooling systems.

In this study, we have addressed reactor-powered and combustion-powered multimegawatt, burst-mode, space power systems to evaluate the effect turbine inlet temperature will have on their performance and mass. Both systems will provide power to space-based antiballistic missile weapons that require hydrogen for cooling, and both use this hydrogen coolant as a working fluid or as a fuel for power generation. The quantity of hydrogen needed for weapon cooling increases as the weapon's cooling load increases and as weapon coolant outlet temperature decreases. Also, the hydrogen needed by the turbines in both power systems increases as turbine inlet temperature decreases. When weapon cooling loads are above 40% to 50% of weapon power and weapon coolant outlet temperature is below 300 K to 400 K, the weapon needs more hydrogen than the turbine in either the reactor- or combustion-powered systems using turbine inlet temperatures at or below the limits of current materials. There is therefore very little system mass reduction to be gained by operating a burst-mode power system at a turbine inlet temperature above present material temperature limits unless the weapon's cooling load is below 40% to 50% or coolant outlet temperature is above 300 K to 400 K. Furthermore, the combustion system's mass increases as turbine inlet temperature increases because oxygen inventory increases.

A superconducting rotor cooling system for an electrical generator includes a free vortex type pump which is located within and forms an integral part of the rotor assembly. The free vortex pump takes advantage of the centrifugal force of rotation of the cooling fluid to help the rotor winding compartment to remain in a superfluid helium state. Improved cooling results from combined natural convection, as occurs in a conventional rotor, and the superfluid heat transport which occurs at the velocity of sound. Patents. (JHD), Supersedes PAT-APPL-107 197-87.

The EPR instrument includes an X band klystron used to generate microwave power that is transmitted to a superconductive waveguide cavity resonator. The cavity is placed between the pole pieces of a large d-c magnet and small a-c magnetic coils energized by a modulation signal source. A microwave crystal detector detects RF energy outputted from the cavity. The detector output is amplified, rectified and filtered in a phase sensitive filter that uses the modulation signal source as a reference. The resultant signal is recorded by an amplitude vs. time recorder. The superconductive cavity includes an inner wall of high-temperature superconductive material, a liquid coolant and an insulating sleeve that passes through the cavity. The specimen to be analyzed is placed in the sleeve. Patents application. (JHD)

An electroforming method is described for making a cooled segmented aperture (SAM) mirror suitable for use with high energy laser irradiation. The method avoids the problems associated with discrete segment SAMs by using electroforming to fabricate a continuous faceplate having a surface shape of the desired array of segments and coolant channels just below the optical surface to provide improved performance under high energy laser irradiation. A master mirror is fabricated from discrete segments. Raised circular lands on the rear of the segments aid alignment of the segments. A negative faceplate is electroformed on the master mirror. A positive faceplate is electroformed on the negative faceplate. Cooling channels are electrical discharge machined into the back of the positive faceplate and additional material electrodeposited to close the channels. A manifold for coolant flow through the cooling channels and bosses for safety screws are attached to the back of the positive faceplate and held in place by a further electrodeposition. Large substrates are epoxy bonded to the electroformed negative and positive faceplate deposits before separation from their respective masters to prevent elastic deformation of the deposits. Separator bars are used to facilitate separation. The structure of the CSA mirror made from the method is also disclosed., Supersedes PAT-APPL-048 110-87, AD-D013 428.

The invention comprises a compact, light weight, dual mode heat transfer device. The dual mode heat transfer devices provides for air cooling of heat dissipating electronic components at moderate aircraft speeds and when the available ambient air is below a preselected temperature. At elevated aircraft speeds and when the ambient air temperature is above the preselected temperature a coolant liquid is converted to steam or vapor in order to cool the heat dissipating components. A preferred embodiment of the invention includes a cold plate for conducting heat away from the heat dissipating components and radiator fins for dissipating cold plate heat to a cooling air flow. Additionally, a liquid coolant is provided in cavities formed in the cold plate immediately adjacent to the electronic components. This liquid coolant vaporizes at elevated temperatures, when the cooling air flow is unavailable, to cool the cold plate. The steam released by vaporization of the liquid coolant is exhausted from the dual mode heat transfer device through a hydrophobic filter membrane covering a portion of the cavities. The hydrophobic membrane is impervious to liquids but permeable to gas., Supersedes PAT-APPL-804 193-85, AD-D012 156.

A flow attenuator is described which is utilized to direct coolant flow to liquid cooled laser mirrors and in so doing substantially eliminates the liquid flow induced jitter generally associates with such flow. The flow attenuator has a housing in which is formed a centrally located passageway. The passsageway branches into a plurality of substanially radially extending contoured chambers. A distribution screen is removably interposed between the passageway and the chambers in order to substantially reduce the 'noise' within the coolant liquid as it passes through the attenuator to the laser mirrors. (Authors), Supersedes PAT-APPL-272 441-81, AD-D008 874.

High power optically activated switches of the semiconductor type utilizing a broadbanded flashlamp as the source of light for rendering the semiconductor conductive and thus close the switch. In order that the conductivity of the semiconductor when in the on state be uniform over the load current carrying cross-section thereof, the semiconductor is treated to produce a tapered density of trapping or re-combination centers therein, with the density being a maximum at the semiconductor surface which faces the flashlamp. Several novel configurations of these switches are shown, including reflectors for concentrating the flashlamp output on the semiconductor, and a plurality of semiconductor switches all activated by a single light source, as well as liquid cooled semiconductors. (Author)

A high energy laser mirror-heat exchanger is described which comprises a faceplate supporting a mirrored surface, a manifold plate adjacent the faceplate and defining a plurality of passageways for distributing fluid coolant to the adjacent faceplate surface, a heat exchanger adjacent the manifold plate having a plurality of wall members configured in a isogrid configuration which may define a plurality of triangularly shaped passageways therebetween for conducting coolant to the manifold plate the intersections of said wall members defining a plurality of insulated passageways for conducting coolant away from said manifold plate, and a backing plate attached to the heat exchanger including coolant inlet and outlet means. (Author), Supersedes PAT-APPL-339 257-82, AD-D009 365.

A shock-mounted, liquid cooled plate assembly for dissipating heat from electronic package mounted on it. A U-shaped cold plate is cast about a tube to provide a passageway for carrying a turbulent flow of coolant along its length. The cold plate is mounted on a vehicle frame by shock-mounted isolator studs which are encapsulated in an elastomer and contained in a housing secured to the frame. An electronic package is mounted on the cold plate by a flange on the package which makes intimate contact with the surface of the cold plate for maximum heat transfer capability. (Author), Supersedes PAT-APPL-834 739-77, AD-D004 774.

A CO2-powered system for cooling garments by conduction cooling when the wearer is subjected to heat stress is provided. A dry ice refrigerant source provides the cooling and the CO2 gas given off during sublimation of the dry ice provides the motive power for a diaphragm type pump which transports heat transfer liquid between the heat source and the refrigerant or heat sink. The system may be interfaced with brine type cooling systems used for food preservation to maintain food temperatures under emergency conditions such as power outages due to its non-electrical energy source. (Author), Supersedes PAT-APPL-918 203-78, AD-D005 232.

The patent application relates to a fluid-cooled electrical conductor having excellent heat transfer, low eddy loss, and good space factor is made by encapsulating small magnet wire strands, which constitute an electrically conductive member, in a meltable matrix that supports the wire; wrapping the matrix with an insulating tape having a silicone adhesive backing and thereby forming an insulating member that surrounds the matrix; perforating the insulating member so that an inlet and an outlet are formed through which an insulating coolant fluid can flow; and, heating, melting, and removing the meltable matrix.

The present invention provides an improved cooling arrangement for a standard electronic plug-in module assembly having a plurality of standard modules supported in grooves in parallel side plates. Each module has a metallic heat plate which facilitates the transfer of heat from the electronic components to the parallel metallic sides which support the modules. A spring is provided in each groove in the side plates for upwardly biasing each module. A top cold plate is forced downwardly by a screw-operated wedge plate and this cold plate engages a metal frame on each electronic module. The springs in the grooves are compressed and apply a force which insures good contact between the cold plate and each frame of each module thereby facilitating transfer of heat away from each electronic module. The top plate is provided with passages for carrying a cooling liquid for removing heat transferred from the modules to the top plate. It is therefore a general object of the present invention to provide an improved cooling arrangement for an electronic plug-in module assembly.

The patent relates to a heat exchange system whereby heat transfer is accomplished by having two adjacent chambers with an outside partition of a first chamber made of heat conductive material for conducting heat inwardly into the first chamber which has a coolant liquid flowing through it. A second chamber has a gas at a pressure higher than the water in the first chamber. A partition between both chambers is made of a gas porous material so that the gas in the second chamber penetrates the connecting wall and flows through the coolant liquid breaking up the formation of liquid coolant film on the heat conductive material.

Experimental and analytical work have been performed to investigate capabilities and thermal performance characteristics of cold plates for electronic equipment cooling. The effort includes air-cooled cold plates, liquid-cooled cold plates, and cold plates provided with heat pipes. Different designs were selected for each of the three categories and thermal tests at different coolant flow and equipment power dissipation rates performed. It has been shown that large amounts of equipment waste heat can be removed by this cooling technique, and thermal performance accurately predicted, particularly with computer-aided analysis. (Author)

The Navy Clothing and Textile Research Facility (NCTRF) has developed a bench-model, dry-ice, liquid-pulse-pump, portable cooling system which has a potential total cooling capacity of approximately 880 kcal (6.77 kg. dry ice) and weighs 9.56 kg. uncharged with dry ice. The system is designed for use with commercial liquid cooling garments to provide conduction cooling to personnel subjected to heat stress.

This report presents the results of a program to design and fabricate an unshielded actively cooled structural panel for a hypersonic aircraft. The design is an all-aluminum honeycomb sandwich with embedded cooling passages ordered to the inside of the outer moldline skin; the coolant is a 60/40 mixture of methanol/water. The panel was mass optimized to sustain 20000 cycles (5000 x scatter factor of 4) of + or - 210 kN/m (+/- 1200 lbf/in.) inplane loading combined with a 6.9 kPa (+/- 1.0 psi) uniform pressure while subjected to a 136 k W/m (12 BTU/ft(2) uniform beat flux. Six fatigue specimens, of critical panel areas, were fabricated by McDonnell Aircraft Company and tested (at room temperature) by NASA. A representative test panel was not fabricated because of problems with the plotting/soldering process. The overall finding is that an actively cooled structure appears feasible for application on a hypersonic aircraft, but the fabrication process is complex and some material and manufacturing technology developments are required. Results from the program are summarized in the body of the report and supporting details are presented in several appendices. (AN)

The use of solar energy for home heating and cooling is often considered to be environmentally benign and to present few or no health hazards. However, all technologies impact the environment, and all can introduce situations that lead to personal harm and property loss. Environmental impact and hazardous situations can be minimized if the needed information is identified and communicated to users and designers during the early development stages of a technology. The goal of this program is to provide a single reference source of hazardous properties and environmental effects of materials used in solar heating and cooling for heat transfer fluids, insulations, seals and sealant materials, glazing material, collector material, and storage material. Hazardous properties that are emphasized are those related to toxicity (using Durham and Gasselin rating schemes) and fires (using rating schemes for Health Hazard Identified for Firefighters, Flammability Hazard Identified for Firefighters, and Reactivity/Stability Hazard Identified for Firefighters). Chemical characterizations of some materials are presented and environmental effects are surveyed. This interim handbook is the first of several editions. Comments and suggestions for improvement are solicited from qualified spokespersons. New data and expanded treatments will follow in later editions. (AN)

This report presents the results of a study to design and fabricate a radiative actively cooled panel. The panel assembly consists of an external thermal protection system (metallic heat shields and insulation blankets) and an aluminum honeycomb structure.

The effectiveness of microclimate cooling systems in alleviating the thermal burden imposed upon soldiers by the wearing of chemical protective clothing under varying environmental conditions has been examined in a series of studies conducted by the U.S. Army Research Institute of Environmental Medicine on the copper manikin, in the climatic chambers and in the field. Liquid-cooled undergarments (LCU) and air-cooled vests (ACV) were tested under environmental conditions from 29 C, 85% rh to 52 C, 25% rh. These parameters were chosen to stimulate conditions which may be encountered in either armored vehicles,or in desert or tropic climates. We have reviewed seven studies using LCU (including two ice-cooled vests) and six studies using ACV. LXU tests investigated the effect on cooling when the proportion of total skin surface covered by the LCU was varied. ACV tests examined the effects on cooling during different combinations of air temperature, humidity and air flow rates. Additionally, these combinations were tested at low and moderate metabolic rates. The findings from these LCU and ACV studies demonstrate that a) cooling can be increased with a greater body surface coverage by a LCU and b) evaporative cooling with an ACV is enhanced at low metabolic rates with optimal combinations of air flow rates and dry bulb/dew point temperatures, resulting in the extension of tolerance time. The application of these findings to industrial work situations is apparent.

Natural convection liquid cooling of simulated electronic components was investigated. A single column of eight protruding components was constructed using foil heaters mounted on the back of stainless steel rectangular blocks. These components were attached to a vertical plexiglass wall to simulate a column of 20 pin DIP's. A channel was formed by placing a smooth movable shrouding wall parallel to the test surface. The test surface and the shrouding wall were placed in a water immersion bath. Flow visualization was accomplished using a laser generated plane of light to illuminate suspended particles. Photographs were taken of the flow at the test surface mid-plane for four different power settings at each of three different channel widths. A nondimensional temperature and a modified Grashof number for each heated protrusion at each input power setting and channel width were determined. Keywords: Immersion cooling; Protruding heat sources; Vertical channels; Flow visualization.

A flow visualization study of natural convection in a liquid filled rectangular enclosure with a small heater protruding into it from one vertical wall was conducted. The top and bottom horizontal surfaces of the enclosure were heat exchangers whose temperatures could be varied independently. The fluid in the enclosure was water. The Baker electrochemical technique which utilizes a pH indicator was used for flow visualization. Photographs were taken of the two dimensional flow for three different locations of the heater on the vertical wall. Nusselt numbers for each heater location and for a range of Rayleigh numbers were also determined. Visual results indicate the presence of a dual-cell configuration within the enclosure. There is a buoyancy driven upper cell and a shear driven lower cell. The flow of the upper cell follows the geometry of the enclosure. Though the uncertainty inherent in the experiment was high data calculations suggest a trend that as the heater is raised within the enclosure the Nusselt number decreases. (Author)

Further miniaturization of high-power semi-conductor devices utilizing silicon disks larger than 12 mm. requires major innovations to improve the average thermal impedance and surge capability. The high thermal impedance in existing discrete devices is caused mostly by the dry interfaces necessary to provide stress relief. This report presents a unique approach to solving the dry interface problem. It describes the design, fabrication and evaluation of a smaller, lighter, electrically isolated dual thyristor module featuring structured copper, solder bonding, polyimide passivation, direct bonded copper on beryllium oxide and a hermetic sealed aluminum case. Details of the SCR modules evaluation in a 60 KVA single channel VSCF electrical generating system are included. (Author)

Two commercially available liquid cooling systems (LCSs) were tested on subjects wearing the current USAF groundcrew chemical defense ensemble and working in the heat. Each cooling system consisted of an ice-water heat sink, a pump, and a vest or vest-and-cap through which cool water circulated. Subjects walked on a treadmill to produce a time-weighted metabolic rate of about 480 W. Environmental conditions were: hot = 45/31C and warm = 32/22C. Under the hot conditions neither LCS produced and difference from the uncooled control, and all subjects were forced to stop within 40-50 min because of high temperatures, excessive heat rates, or exhaustion. Under the warm condition the LCS did allow T sub re to equilibrate; one system which could be recharged with ice enabled subjects to continue work to the 160-min limit of the protocol. Discussion covers logistics problems and reliability of the two systems. The conclusion is the LCSs are a viable concept for USAF operations, but that better heat sinks must be found and field tested before acceptance.

The Navy Clothing and Textile Research Facility (NCTRF) conducted a field evaluation to compare two life-support-suit assemblies. One assembly was a liquid-air-cooled suit that provided convective cooling; the other was a dry-ice system that used liquid-cooled underwear to provide conductive cooling. The test results indicated the dry-ice system was preferred by 74.2% of the test subjects for cooling purposes. (Author)

A Self-Regulating Transpiration System (SERTS) concept has been developed through the design of ground test and flight hardware by means of which the nose tip of a reentering missile might retain its sharp shape. The concept uses the thermal expansion of a liquid to open a valve through which a liquid coolant flows, admitting the coolant to a vaporization chamber. Aerodynamic heating of the nose tip causes the actuator temperature to rise, opening the valve and permitting the coolant to absorb the heat input. The vapor so generated is expelled into the boundary layer so the heat transfer to the nose tip will be diminished by blowing. A successful ground test has been made at A.R.A.P. (Author)

An infrared spectrometer used to obtain atmospheric emission spectra from a rocket at altitudes between 45 and 200 km in the ICECAP Auroral Measurements Program is described. The instrument continuously scanned the 6.75-23.2 micrometers spectral region at the rate of 2 scans per second. The instrument resolution of the spectrometer, which employed a circular-variable interference filter (CVF), ranged from 3 to 4 percent.

This report describes the development of an ultraminiature, Vuilleumier (VM) cycle, cryogenic refrigeration system for infrared type systems. The refrigerator that was designed and fabricated is a liquid cooled machine producing 0.75 watt of refrigeration at 77 K in an ambient environment of 80 F. The system consists of the refrigerator, a solid state electronic temperature controller, and an auxiliary cooling supply. Major design objectives were to make the refrigerator as small as possible and adaptable to gimbaled applications. The refrigerator consists of a small thermal compressor, which would normally be mounted off-gimbal, and a pneumatically driven expander, which would normally be mounted on-gimbal. A single capillary line (0.030-inch I.D. x 12-inch length) connects the two elements. The compressor weighs less than 4 lb and fits in an envelope 2 inches in diameter x 3.4 inches long; the expander weighs less than 0.05 lb and fits in an envelope 0.75 inch in diameter x 1.6 inches long. (Author)

Tests were performed and incorporated into engineering models to provide solutions to the problems experienced in operational characteristics of lamps being used in the field. The work consisted of redesign of the electrodes and application of new methods of manufacturing and inspection to provide increased life and reliability during operation. A unique design evolved which combines a depressurization sub-system integral with the lamp and compatible with the airborne environment for increased safety for operating personnel. The lamp design was successfully tested to meet the optical and environmental requirements, and a pilot production run successfully completed to provide a manufacturing capability for the military requirements. A plan for emergency mobilization was provided which would increase production to 50 lamps per week. (Modified author abstract)

A nitrogen-cooled rocketborne radiometer design and system test evaluation are given. The instrument uses an indium antimonide photovoltaic detector with a 77K background. The entire optical subsection of the instrument, including detector, filter, chopper, and lens is cooled to near 77K.

A series of small-scale model rocket tests was performed to evaluate the acoustical performance of water-cooled flame buckets. Data collected from these tests indicated the change in sound pressure level is a function of water flow-rate ratios for locations in both the near and far field.

This report describes the analysis, design, fabrication, and test of water-cooled segments to define the most suitable injector configurations and combustion chamber geometries for 25,000-pound-thrust, O2/H2, lightweight, aerospike thrust chambers. Two-hundred and seventy-one hot-fire tests with numerous injector and chamber configurations were conducted at chamber pressures between 140 and 988 psi. The injector development was supplemented with cold- flow tests of single injection elements. High measured performance was demonstrated in low-volume combustion chambers (3.0-inch length from injector face to the throat).

Technical and economic data were developed in three categories: heat sinks, miscellaneous cooling-system components, and refrigeration and dehumidification devices. Various combinations were considered as assembled into cooling systems and these systems were then evaluated with respect to their cost effectiveness in removing excess shelter heat. Special attention was given to the conception of applicable new cooling systems. A comparison is also made of the advantages, disadvantages, and estimated costs associated with various conventional and novel systems. Areas of needed research are defined for the development of novel systems.

Subcooling liquid refrigerant in a vapor compression refrigeration cycle increases the system capacity. The purpose of this thesis is to relate theoretical and experimental performance characteristics to one method of subcooling Refrigerant 12, the use of a liquid-vapor heat exchanger. Theoretical and experimental values of system coefficient of performance and horsepower per ton are found at various evaporating pressures for a system with and without a liquid-vapor heat exchanger. The theoretical performance of a system with an evaporating pressure of 26 psia and a condensing pressure of 110 psia is found for variations in heat exchanger effectiveness between 0 and 1.

Methods of controlling equipment temperature rise in airborne compartments at supersonic flight speed are investigated. Design and performance data for expanded ram air cooling systems and various types of fuel cooled equipment cases are presented for steady state thermal operation. Other methods of controlling temperature rise are analyzed for transient thermal performance and design procedures for their applications are developed. Calculation methods are given in detail. Design procedures are illustrated by examples. The performance characteristics of the following methods are investigated (1) insulation of equipment compartment walls without cooling, (2) insulation of individual equipment items, (3) fuel jacketing of equipment compartments, (4) cooling of the compartment atmosphere by means of a central fuel cooled heat exchangers, (5) cooling of individual equipment items by installation on a fuel-cooled plate, and (6) cooling of individual equipment items by evaporation of an expendable coolant. Methods of analysis and criteria for the selection of specific means for the control of temperature rise are emphasized. The large number of variables by which each practical situation would be defined does not permit a concise description of the optimum range of conditions for the application of each method.

An extensive investigation of the cooling characteristics of a multicylinder, liquid-cooled aircraft engine of 1710-cubic-inch displacement was conducted at the NACA Cleveland laboratory. The results of this investigation are presented showing the variation of the cylinder-head temperature and the coolant heat rejection with the pertinent engine and coolant variables. The data, which were obtained on five engines, are presented for power outputs up to 1860 brake horsepower, coolant flows from 50 to 320 gallons per minute, and wide ranges of engine speed, manifold pressure, fuel-air ratio, inlet-air temperature, ignition timing, exhaust pressure, and coolant composition, temperature, and pressure. The ranges of variables included operation into the boiling range of the coolant for which various phenomena are described.

Investigations showed that for the range of angles of attack and boundary layer profiles at various fuselage stations the maximum displacement thickness was nearly 1.2 in and was at the most rearward station. The displacement thickness was found to be greatly affected by the pressure gradients over the windshield-canopy combination and in the wing-fuselage juncture. An average value for the shape parameter between 1.3 and 1.4 was obtained for the turbulent boundary layer.

The AN/TVS-3 30-inch xenon searchlight was studied in Vietnam to describe and evaluate the tactical employment of the searchlight and to determine its maintenance requirements. The 30-inch xenon searchlight is mounted on a two-wheel trailer; it is both liquid- and air-cooled.

IN ORDER TO STUDY THE EFFECTS OF ELEVATED IRRADIATION TEMPERATURES UPON THE SHIFT (increase) in the ductile-to-brittle transition temperature of two pressure-vessel steels, an experimental assembly containing four groups of specimens was irradiated. Four different irradiation temperatures, 260, 400, 450, and 550 F, were maintained for a one-month irradiation period. Post-irradiation evaluation of specimens indicated no significant temperature effect for the materials irradiated at less than 450 F. There was a significant effect as a result of irradiation at 550 F, the shift being roughly 100 F less. The transition-temperature shifts for materials irradiated at less than 450 F were in good agreement with data from 19 earlier experiments in which the specimen temperatures during irradiation were less than 200 F.

An outline is presented of recommendations on design features for Ti- and Zr-melting furnacs. Special emphasis was placed on safety features. A standby cooling water system with instrumentation to indicate its serviceable condition was a principal requiremet. Positive protection of personel by a vault-type design was recommended with mechanical clamping of the furnace assembly and components, and a pressure relief device. Vacuum pumps should be vented outside the building to prevent accumulation of the hydrogen. Safety features for the crucible or molds are enumerated as well as automatic devices for sensing the lack of water discharge and for cut off of electric power to the arc. A number of warning devices and instruments for visual observation or recording critical operating parameters are included.