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By Amey S. Majgaonkar, M.E.

Amey S. Majgaonkar, M.E., is a senior engineer at Kirloskar Pneumatic Company Limited, in Pune, India. He is a member of ISHRAE.

About the Author

Refrigeration for ShipsNaval refrigeration applications are similar to a high-rise building, only

laid on its side. However, naval applications must deal with a corrosive

marine environment, limited space for equipment, and the movement of the

ship. This article describes the many additional constraints a designer faces

in refrigeration system design for naval applications.

The standards referred to in this article are case specific and can be used only after agreement with that particular navy. Usu-ally, each navy uses standards per its own re-quirements on a case-by-case basis. In many cases, navies allow equivalent or similar standards for equipment and raw materials after a detailed study of project specification requirements regarding improvements in system design and operation.

Calculating Refrigeration Capacity Refrigeration plants are used onboard

mainly for food preservation in cold rooms and for producing ice required for

onboard consumption. Heat load calcula-tions provide the refrigeration capacity required for cold rooms. Heat load can be calculated by using methods available in technical literature or by using commer-cial software. The ASHRAE Handbook—Fundamentals and ISO Standard 75471 are useful for this purpose. The required capacity of a refrigeration plant is deter-mined from individual cold-room heat load, ice production load, and from the required cooling down period. Generally, the refrigeration plant on warships has a capacity in the range of 3.5 kW to 50 kW (1 ton to 14 ton).

For chiller packages in most cases, a navy will specify the required capacity, or capacity can be calculated from chilled water flow rate and temperature difference. The capacity usually is in the range of 35 kW to 2,700 kW per chiller package.

RefrigerantIn developing countries, R-22 will be

phased out soon. The service life of older ships is being extended to 10 to 12 years by retrofitting them with better plants, equipment, instruments, and machines. R-12 systems are being replaced by R-22 systems because the plant size is smaller compared to an R-134a replacement system. For new ships, environmentally friendly R134a is preferred.

Limited SpaceAs stated previously, a ship is similar

to a high-rise building, only laid on its

The following article was published in ASHRAE Journal, December 2008. ©Copyright 2008 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. It is presented for educational purposes only. This article may not be copied and/or distributed electronically or in paper form without permission of ASHRAE.

Dec ember 2008 ASHRAE Jou rna l 51

side. Hatches, openings, passages, and staircases interconnect the compartments. The refrigeration plants and chiller pack-ages are normally installed in any of these small compartments located in forward, aft (rear), and the mid portion of a ship, depending upon function. These compartments contain ad-ditional equipment, pipelines, and electrical cables, restricting the available space.

A feasibility study considering the following points is es-sential for retrofits and is useful when designing new plants. The plant and equipment must be compact enough to be ac-commodated in the available space. The shipping route of indi-vidual equipment and/or a complete plant must be considered before designing the individual equipment or complete plant. The plant’s orientation within the compartment is decided after carefully considering its operational and maintenance requirements, and the best use of existing pumps and piping and electrical cabling. The mounting arrangement is decided by considering the foundation, bulkhead, deck head supports, and stiffness.

Once the sizes, weights, and operational requirements of individual equipment are known and, after considering all the previous points, the positioning and assembling of the indi-vidual equipment is done to form a compact skid to fit in the available space.

Equipment WeightThe equipment designed for naval use is expected to be lighter

and stronger. The size and material of construction decides the weight of the equipment. Reduction in weight is possible by reducing the size and using lighter construction materials, keep-ing its operational and functional requirements intact.

Equipment such as heat exchangers and pressure vessels carry operating fluids. The weights for the equipment are specified as empty and operational in their datasheets. Standard engineer-ing practices and international standards from the American Society of Mechanical Engineers (ASME), Tubular Exchanger Manufacturers Association (TEMA) and ASHRAE assist in optimizing the size and weight of such equipment.

Seaway ConditionsThe refrigeration plants and chiller packages are designed to

operate satisfactorily under the seaway conditions of rolling, pitching, heave, yaw, tilt, list, and trim. Seaway conditions are an important consideration when locating and positioning plants within the compartments.

Advanced computer analysis can assist in simulating and predicting the equipment performance under equivalent seaway conditions. Before designing, it is important to understand the flow behavior of fluids in the equipment under seaway condi-tions. The major causes of failure/unsatisfactory performance of refrigeration plants and chiller packages under seaway conditions are insufficient oil flow to compressor, improper separation of oil in an oil separator, malfunctioning of level switches, and inefficient heat exchange in heat exchangers. These aspects are considered by performing an actual tilt test

in different directions, periodically recording operational and safety cutout parameters.

Environmental ConditionsInstruments and controls must be selected considering the

range of temperature and pressure encountered during ship operation. For example, if seawater is used as the cooling medium in a condenser, the range of thermostatic expansion valves must be properly selected considering the variation in seawater temperatures. As in the case of extremely low seawater temperature, the pressure drop across an expansion valve may not be sufficient for desired flow rate of refrigerant.

Seawater-cooled condenser design must consider these con-ditions. The seawater pumps, piping, valves, fittings, and flow meters must be properly selected considering these changing environmental conditions. Instruments such as some flow meters need recalibration with changing environmental condi-tions. During sailing, this is difficult, care must be taken when choosing suitable and proven instruments.

ShockWarships and submarines are mainly exposed to two types

of shocks: 1) underwater explosion (underwater shock) and 2) the reactive force caused by firing a missile from the ship. The underwater shock is critical.

Severity of shock depends upon magnitude of the explosion, location of the equipment and its supports, and duration and propagation of the shockwave. Each navy specifies different shock grade environments for various types of equipment on a case-by-case basis. The equipment and machinery supplied for naval use must be able to withstand the specific shock and perform satisfactorily after a shock.

Effects of ShockShock has the potential for damaging the plant or the plant’s

equipment.Brittle or fragile items can fracture and ductile items can •bend due to shock. Some items may not be damaged by a single shock but will experience fatigue failure with many repeated low-level shocks. Shock may result in only minor damage, which may not •be critical. However, cumulative minor damage from several shocks will eventually result in the equipment/plant being unusable. Shock may not produce immediate apparent damage but •might cause the service life of a part such as a compressor to be shortened, and reliability is reduced. Shock may cause parts to fall out of adjustment (e.g., •couplings between compressors, motor, some precision instruments, etc.).

Designing for ShockDesign using shock calculations. A navy will specify the shock

environment for a particular class of ship and submarine and provide the related shock grade curve. The amplitude and duration of shock

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can be traced over this curve with respect to equipment weight. If the equipment or assembly is simple, then shock calcula-

tions can be done manually using the procedure mentioned in the BR 3021 standard.2 For complex assemblies, a finite element analysis using commercial software can be done.

The results of these calculations and analysis are useful in predicting the failure of components parts, joints, etc. The weaker sections can be discovered and necessary modifications in the design are performed until design requirements are met for proper post-shock functioning of equipment.

Reduce shock transmitted to equipment. It may not always be practical or economical to design all items of machinery and equipment to withstand the maximum imposed acceleration due to shock, it is necessary in many cases to protect these items by using suitable shock mounts.

Using flexible bellows/rubber expansion joints, and multi-stage structures also reduces the shock transmitted. Position the mounts so the height of the center of gravity above the plane-of-fixing of shock mounts does not exceed half of the minimum span of mounting.

Perform a physical shock test. For a number of similar plants and equipment, a prototype plant and/or equipment is shock tested by a noncontact underwater explosion in its proximity or by a physical shock test on a shock testing machine. The prototype plant and/or equipment are examined for failures, and the necessary design modifications are done until the prototype successfully passes a shock test without any major physical failure. Post-shock, performance of the prototype plant and/or equipment is checked against acceptable conditions in the performance test. The tested prototype plant and/or equipment is then yellow-banded and never used onboard.

Brittle materials like grey cast-iron or any material having an elongation capability of less than 10% should not be used for naval equipment, as they are more prone to failure under shock conditions. However, if the equipment passes the speci-fied shock test and stresses are proved within acceptable limits the brittle material can be used.

Structure-Borne VibrationVibration refers to mechanical oscillations about an equilibrium

point. The medium in which sound (vibration) exists often is de-scribed by airborne, waterborne, and structure-borne. Vibrations are undesirably produced due to unbalanced forces in reciprocat-ing and rotating machinery such as the compressor used in the refrigeration plant and chiller packages. The unbalanced forces are generated due to imperfect design, manufacturing, assembly, installation, operation and maintenance. The vibration causes failure of components, parts, or assemblies. The vibrations may also be detected by an enemy. A navy will specify the acceptable limits for structure-borne vibrations. The refrigeration plant and chiller package designed must conform to these requirements.

For any vibrating structure, when vibrating frequency matches with its own natural frequency, resonance occurs. At resonance, the amplitude of vibration increases, and if it crosses the tolerable limits, the structure fails.

Typically for naval applications, the structure-borne vibra-tions are measured as per MIL-STD-740-2.3 This standard pro-vides scope, purpose, application, implementation, approach, measurement procedure, and acceptance criteria for different types of naval equipment mounted in different methods such as resiliently/solid, etc. In some cases, the mechanical vibration requirements for plants and equipment are to be in accordance with MIL-STD-167-1.4 Type I is associated with environmen-tal vibration, and Type II is associated with internally excited vibration. All equipment must withstand, without any reduction in reliability and performance, the effects of environmental vibration as defined by MIL-STD-167, Type I. The dynamic stiffness of mounts must not exceed the levels specified by a navy, and above-mount, narrow-band vibrations levels must be below the one-third octave levels specified by a navy.

The analysis of vibration data reveals the source of vibration, its transmission path, and probable occurrence of failure. The vibrations can be minimized from these results in following ways (also see sidebar “Tips for Reducing Vibration.”):

Minimizing vibrations produced by source. In refrigeration plants and chiller packages, the only moving parts are the com-pressor and motor, pump and pump motors, fan, and air-cooling unit motor. The reduction in speed of rotation minimizes the vibrations. Use of semi-hermetic compressor, flexible coupling, and mono-block pump reduces the vibrations. Properly lubri-cating the moving parts and operating the plant close to design conditions reduces the vibrations.

Minimizing vibrations in its transmission path. If equip-ment is rigidly mounted/connected, then vibrations pass eas-ily through them. Using multistage structure, shock mounts, and flexible piping rubber expansion joints mitigates the

Tips for Reducing VibrationDesign structure by using FEA analysis. •Provide stiffeners; avoid stress concentration (sometimes •even by drilling holes) wherever necessary.Isolate the moving parts, i.e., vibrating structure from •non-vibrating structure.Provide adequate support to vibrating equipment. •For vibrations isolators, do not use central bolt of longer •distance than the height of mount to avoid direct vibration transmission through central bolt. Tighten the hold-down bolt, and use spring washers at •appropriate places.Provide support for pipes cables using special clamps with •internal rubber lining to avoid damage due to friction.Use flexible coupling. •Keep required tension in the belts. •Do quality welding and brazing. •Do proper lubrication of moving parts. •Use rubber paints and standard painting procedure. •Follow a condition-based monitoring program. •Undertake active vibration isolation. •

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vibrations. Proper surface finish, good workmanship, proper lubrication of moving parts, and use of rubber paints mini-mizes the vibration.

Airborne Vibration (Noise). Noise is unpleasant or un-wanted sound. The sources of noise in refrigeration and chiller packages are the motor, compressor, pumps and fans. It occurs as a by-product of vibration.

Certain noises are irritating and can seriously affect efficiency and health. Noise also may be detected by an enemy. A navy will specify the acceptable noise levels for equipment.

The airborne sound power level radiated by the auxiliary equipment is expected to comply with the levels stated in MIL-STD-1474D.5 Airborne noise measurements are taken as sound pressure level reference of 1e-12 W at 1 m (3 ft) distances from equipment in one-third octave band over a frequency range of 10 Hz to 10 kHz. Noise levels are measured at 25%, 50%, 75%, and 100% rated output at six positions around the plant. Typi-cally for a naval application, the airborne noise is measured as per MIL-STD-1474D.

Any noise problem may be described in terms of a sound source and transmission path and noise control may take the form of altering any one or both the elements. When considered in terms of cost effectiveness and acceptability, experience puts modification of the source well ahead of modification of the transmission path. In existing facilities, however, the modifica-tion of the transmission path is the only feasible option.

The application of the noise reduction techniques in the “Tips for Controlling Noise” sidebar may not result in significant noise reduction if the fundamental science of noise is not considered when applying these techniques.

As a general rule, control of airborne noise is possible by opti-mizing radiation directivity by placing the radiating openings in remote areas and fitting them with silencers/screens and control of structure-borne noise is possible by reducing the surface of radiating parts and reducing the radiation efficiency (decrease the thickness of plates or use perforated plates).

Minimum rate of change of force is associated with minimum noise. Since noise is a result of energy waste due to friction,

Tips for Controlling NoiseTips for Controlling Noise at Its Source

Substitute equipment or parts of equipment: use rotating •machines rather than reciprocating machines, e.g., screw compressor instead of reciprocating compressor, semi-hermetic compressor instead of open-type compressor, modification of gear teeth, and screw profiles. Maintenance: balancing and lubrication of moving parts, •replacement or adjustment of worn or loose parts, modifying parts to prevent rattles and ringing.Substitution of materials, e.g., replacing metal parts with •plastic/rubber parts.Change of work methods and layouts. Keeping noisy •operations in the same area, separating noisy operations from non-noisy processes, selecting the slowest ma-chine speed appropriate for a design duty conditions. Reduction of resonance noise. Ensure that machine •rotational speeds do not coincide with resonance fre-quencies of the supporting structure by changing the stiffness or mass of the supporting structure. Reduction of acoustic radiation efficiency: e.g., replace- •ment of a solid panel or machine guards with a mesh or perforated panel, or use of narrower belt drives.Reduction of noise resulting from fluid flow. Provide •machines with adequate cooling fins so that noisy fans are no longer needed. Use fan blades designed using CFD software to minimize turbulence, increasing the number and width of fan blades, reducing the thickness of fan blades. Use centrifugal, rather than propeller fans. Locate fans in smooth, undisturbed airflow. Use large low-speed fans rather than smaller faster ones. Minimize the velocity of fluid flow. Maximize the cross-section of fluid streams, Reduce pressure drop across any one

component in a fluid flow stream. Minimize fluid tur-bulence where possible (e.g., avoid obstructions in the flow). Choose quiet pumps in hydraulic systems avoid cavitations. Choose quiet nozzles for compressors. Iso-late pipes carrying the fluid from support structures.

Tips for Controlling Noise in Transmission PathUse sound enclosures for noisy components on a ma- •chine/for a complete system.Vibration isolation of machines from noise-radiating •structures.Vibration absorbers and dampers. •Addition of sound-absorbing material to reverberant •spaces to reduce reflected noise fields.

Tips for Control of Noise at ReceiverUse earmuffs. •Use active noise cancellation techniques. •

Noise Control for an Existing FacilityUndertake an assessment of the current environ- •ment where there appears to be a problem, includ-ing the preparation of noise control contours where required.Establish the noise control objectives or criteria to be •met.Identify noise transmission paths and generation •mechanisms.Rank-order noise sources contributing to any exces- •sive levels.Formulate a noise control program and implementa- •tion schedule.Carry out the program. •Verify the achievement of the objectives of the program. •

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vibration, cavitations, etc., if the plant or machinery operates at its best efficiency, the noise produced is less.

Material CompatibilityDefense standards provide guidelines when selecting the

material of construction for naval refrigeration plant and chiller packages for the marine environment.

The material in contact with corrosive seawater can be gun-metal, cupro-nickel, nickel-aluminum bronze (NAB), titanium, etc. The mechanical properties of these metals such as malle-ability and ductility determine its application in materials like tubes, plates, and supports, etc.

Generally, for seawater cooled condensers, a Cu-Ni (70:30) material is used. Also, seawater pipelines can be made of Cu-Ni (90:10). These materials are expensive and intelligent design will minimize its content in the plant. As a general design guideline, use these materials only for the seawater-contacting surface and for the other assembly use different suitable material (condenser water heads, tube sheets, and seawater tubes).

Depending upon applications and regulations, certain navies prohibit use of some materials, e.g., mercury-based thermom-eters, asbestos-based gaskets, magnetic materials in instruments and controls, etc.

System Design OptimizationThe main aspects that need to be considered when designing

refrigeration plants and chiller packages for naval application have been covered here. A few additional parameters such as interchangeability, flexibility of operation, and ease of maintenance, etc., also must be considered. A proper system design and equipment selection can reduce energy consump-tion dramatically.

Refrigeration system performance depends upon the design of an individual component in the system. The system is only as strong as its weakest component. The system design and equipment selection are cases of optimization influencing fixed and operation costs.

Refrigerant Compressor. The compressor is the heart of the vapor compressor refrigeration system. The refrigeration capacity, evaporating temperature, condensing temperature, and refrigerant type determines the compressor type used. Energy consumption, noise and vibration limits, size, weight, and system type also govern the compressor selection.

Refrigeration systems are always sized slightly more than peak load. During seasonal changes or daily load fluctuation, there is always a possibility of running the compressor on part load. The compressor efficiency decreases at part load, so many compres-sors have built-in capacity control arrangement with solenoid valves. Also, the power factor of induction motors drops when it runs on part load. This results in higher energy consumption. To counter this, separate multiple refrigeration systems are used to take maximum load during normal working conditions.

On warships the refrigeration plant has a capacity in the range of 3.5 to 50 kW (1 ton to 14 ton). Evaporating tempera-tures are in the range of –20°C to –30°C (–4°F to –22°F) and

condensing temperatures are in the range of 38°C to 43°C (100°F to 109°F) with R-22/R-134a as a refrigerant. The most common choices for designer for such duty conditions are open-type reciprocating compressor, scroll compressor or her-metic compressors. For refrigeration plants, peak load occurs when fresh product is loaded in the compartments. Therefore, multiple refrigeration systems are provided. During peak load multiple refrigeration systems can be operated to bring down the temperature of products to storage temperature. Thereafter, a single refrigeration system can be operated to maintain the temperature. To maintain different temperatures inside cold rooms, evaporator pressure regulating valves are provided on individual suction lines of higher temperature rooms before the common suction header.

The capacity of the chiller package lies in the range of 30 to 2,700 kW (8.5 ton to 768 ton). Chilled water outlet temperatures are 6°C to 8°C (43°F to 46°F) and condensing temperatures are 38°C to 43°C (100°F to 109°F) with R-22/R-134a as a refriger-ant. Open-type reciprocating compressors, screw compressors, semi-hermetic, and centrifugal compressors are better suited for such conditions.

In air-handling units, the chilled water is used for condition-ing air. Suitably designing AHUs and controlling airflow rates can achieve the different temperature requirements for various compartments.

Motor. Motors are the prime movers for compressors and pumps. Both ac and dc motors are used for marine applica-tions. In surface ships and nuclear submarines, ac motors are used because ac supply is available on these vessels. However, lack of ac supply on non-nuclear submarines makes dc motors mandatory. Generally, air-cooled motors are used for naval ap-plication. Seawater-cooled motors are also used.

To limit the starting current value, typical ac motors for na-val use are started with autotransformer or star/delta starters. Specification of motors and starters for naval ships are required to comply with standard EED-Q-071 (R3).6 All motors are re-quired to be provided the following protections: single phasing, over-current, under/over voltage, thermal, no-load operation, moisture sensing, and short circuit. Using totally enclosed fan-cooled (TEFC) motors with enclosure protection of IP55/IP56 is common for naval duty. If not tested earlier, a motor is required to be type tested as per specification in the standard EED-Q-071 (R3). Environmental tests such as vibration, high temperature, damp heat, drip proof, mold growth, bump, and shock impact are required to be performed as per JSS 555557 standard. EMI/EMC test is required to be performed as per MIL-STD-461D.8

Condenser. Shell-and-tube type condensers with refrigerant on shell side and seawater on tube side are common for marine applications. Using the latest software with TEMA and ASME standards helps achieve significant saving in condenser manufac-turing, as well as operating cost. When preparing the general ar-rangement and layout drawings, it is important to provide enough space for maintenance and tube cleaning of condenser.

Thermostatic Expansion Valve. The selection of thermo-static expansion valves is particularly important because it

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regulates refrigerant flow to the evaporator. An undersized ex-pansion valve will prevent sufficient refrigerant flowing into the evaporator causing reduction in design cooling capacity of the system and an oversized expansion valve will allow too much refrigerant flow into the evaporator causing liquid refrigerant to flow back to the compressor. If not remedied, both conditions will cause compressor damage.

Evaporator. Shell-and-tube type DX-evaporators are used for chiller packages. In DX-evaporators, fresh water flows on the shell side and refrigerant flows through tubes. Internally serrated tubes are used to increase heat transfer rate and make evaporators compact. The optimum design of an evaporator is done considering velocity, pressure drop and heat transfer rate to achieve saving in evaporator manufacturing and operating cost. When preparing the general arrangement and layout draw-ings, it is important to provide enough space for maintenance and tube cleaning of the evaporator.

Air-Cooling Units. The refrigerant flows in the tubes and air flows over the fins of air-cooling units. Different types of compact air-cooling units are available. In a refrigeration plant its location and mounting must be carefully selected to obtain the desired cooling effect in cold storages. The air-cooling units must be installed inside rooms so that when doors are open, ACUs will not throw conditioned air outside the room and the ACU fan can’t suck in outside air easily. Provision of defrost heaters must be made for low temperature application.

Auxiliary Systems. Auxiliary systems like a chilled water/cooling water system is inherently required with vapor com-pressor refrigeration systems. An optimization approach in designing these systems helps in integrating these systems with the refrigeration system and the ship’s existing water system to reduce overall cost.

Design the condenser for higher cooling water temperature difference, which will mean less flow rate and less pumping power for the same capacity. However, this makes the condens-ing temperature rise resulting in higher compressor power. The temperature rise of 4°C to 6°C (7°F to 11°F) is normally considered.

For chilled water, as well as cooling water circuit, minimizing bends and elbows reduces the pressure drop in water piping. Selecting large diameter and shorter pipes reduces the pressure drop. Selecting large pipe size is costly and further water line valves also becomes costlier with increasing pipe size.

Selection of appropriate pumps is also required to minimize operating cost, reducing cavitations, vibrations and noise.

Piping and Fittings. The refrigerant, chilled water and cool-ing (sea) water piping must be selected by considering material compatibility. The sizes and ratings must be selected to ensure safe operation of the plant for the most expected severe design pressures and temperatures. Avoid pipe threads and reduce number of joints. All debris and weld slag must be properly cleaned and care should be taken so that it will not enter the piping. Ensure that brazed and welded joints are leak-proof by pressure testing.

TestingThe naval refrigeration plants and chiller packages undergo

stringent type test, production test, endurance test, and tilt test, shock test, vibration and noise test, workshop test, and onboard trial. Usually, a navy publishes the specifications, procedures, and requirements for all such tests (statement of technical requirement) along with tender document. The supplier has to prove the plant performance against these requirements.

Remember, that the refrigeration and air-conditioning plants are always oversized, proving the performance does not merely mean obtaining the guaranteed refrigeration capacity. However, it must be ensured that the performance is achieved with less than or equal to the guaranteed power consumption while meet-ing all other peformance parameters such as vibration, noise, etc. Testing ensures reliability of equipment and systems.

Summary Most of the design parameters and constraints for designing

naval refrigeration plants and chiller packages are presented in this article. An attempt is made to explain the designing procedure used and general tips are provided to unfold the secret of better design of naval refrigeration plants and chiller packages.

Better equipment, standards, procedures, softwares, and design guidelines are becoming available within the industry, however, the future of naval refrigeration will remain subjective depending upon the method of application of these resources, judgment of designers, and improvement in technology.

References International Organization for Standardization. 2002. ISO 1.

7547:2002, Ships and Marine Technology—Air-Conditioning and Ventilation of Accommodation Spaces—Design Conditions and Basis of Calculations.

Ministry of Defense, U.K. BR 3021, Parts 1 and 2. 1995. 2. Shock Manual.

U.S. Department of Defense. MIL-STD-740-2. 1986. 3. Structure-borne Vibratory Acceleration Measurements and Acceptance Criteria of Shipboard Equipment.

U.S. Department of Defense. MIL-STD-167-1. 1974. 4. Mechanical Vibrations of Shipboard Equipment.

U.S. Department of Defense. MIL-STD-1474D. 1997. 5. Noise Limits.

Ministry of Defense, India.6. EED-Q-071(R3). 2007. “Specification of motors and starters for naval ships.”

Ministry of Defense, India.7. JSS 55555. 2000. Environmental Test Methods for Electronic and Electrical Equipment.

U.S. Department of Defense. MIL-STD-461D. 19938. . Require-ment for the Control of Electromagnetic Interference Emmissions and Susceptibility.

BibliographyGokhale A. 2008. “Chillers for warships.” ISHRAE Journal

January–March:73 – 82.

AcknowledgmentsThe author wishes to thank Kirloskar Pneumatic Company

Limited, Pune, India, for providing an opportunity to learn and design naval refrigeration and air-conditioning systems.