Module 9 Refrigeration and Stabilizer PDF

Refrigeration, Air- conditioning and Ventilation/Stabilizer Module 09 TOPIC 9.0 Auxiliary Machineries 9.1 Refrigeration, Air conditioning and Ventilation  Difference between Refrigeration and Air Conditioning and Ventilation  Refrigeration cycle operation principle and components  Re...

Refrigeration, Air- conditioning and Ventilation/Stabilizer Module 09 TOPIC 9.0 Auxiliary Machineries 9.1 Refrigeration, Air conditioning and Ventilation  Difference between Refrigeration and Air Conditioning and Ventilation  Refrigeration cycle operation principle and components  Refrigerant Types and Properties  Coefficient of performance  Refrigeration System Arrangement on Board  Air conditioning system Arrangement on Board 9.2 Stabilizer operation and Construction Describes a Vapor-Compression-Cycle of Refrigeration Plant  Vapor Compression Refrigeration Cycle involves four components: compressor, condenser, expansion valve/throttle valve and evaporator.  It is a compression process, whose aim is to raise the refrigerant pressure, as it flows from an evaporator.  The high-pressure refrigerant flows through a condenser/heat exchanger before attaining the initial low pressure and going back to the evaporator. Describes a Vapor-Compression-Cycle of Refrigeration Plant  Step 1: Compression  The refrigerant (for example R-717) enters the compressor at low temperature and low pressure.  It is in a gaseous state. Here, compression takes place to raise the temperature and refrigerant pressure.  The refrigerant leaves the compressor and enters to the condenser.  Since this process requires work, an electric motor may be used.  Compressors themselves can be scroll, screw, centrifugal or reciprocating types. Describes a Vapor-Compression-Cycle of Refrigeration Plant  Step 2: Condensation  The condenser is essentially a heat exchanger.  Heat is transferred from the refrigerant to a flow of water.  This water goes to a cooling tower for cooling in the case of water-cooled condensation.  Note that seawater and air-cooling methods may also play this role.  As the refrigerant flows through the condenser, it is in a constant pressure.  One cannot afford to ignore condenser safety and performance.  Specifically, pressure control is paramount for safety and efficiency reasons. Describes a Vapor-Compression-Cycle of Refrigeration Plant  Step 3: Throttling and Expansion  When the refrigerant enters the throttling valve, it expands and releases pressure.  Consequently, the temperature drops at this stage. Because of these changes, the refrigerant leaves the throttle valve as a liquid vapor mixture, typically in proportions of around 75 % and 25 % respectively.  Throttling valves play two crucial roles in the vapor compression cycle.  First, they maintain a pressure differential between low- and high-pressure sides.  Second, they control the amount of liquid refrigerant entering the evaporator. Describes a Vapor-Compression-Cycle of Refrigeration Plant  Step 4: Evaporation  At this stage of the Vapor Compression Refrigeration Cycle, the refrigerant is at a lower temperature than its surroundings.  Therefore, it evaporates and absorbs latent heat of vaporization.  Heat extraction from the refrigerant happens at low pressure and temperature.  Compressor suction effect helps maintain the low pressure.  https://www.araner.com/blog/vapor- compression-refrigeration-cycle   Describe an Air-conditioning Plant  An air conditioner is a system that is used to cool down a space by removing heat from the space and moving it to some outside area.  The cool air can then be moved throughout a building through ventilation.  https://energyeducation.ca/ encyclopedia/Air_conditioner  Difference between Refrigeration, Air-Conditioning and Ventilation  Refrigeration, or cooling process, is the removal of unwanted heat from a selected object, substance, or space and its transfer to another object, substance, or space. Removal of heat lowers the temperature and may be accomplished by use of ice, snow, chilled water or mechanical refrigeration.  Air-conditioning is that process used to create and maintain certain temperature, relative humidity and air purity conditions in indoor spaces. This process is typically applied to maintain a level of personal comfort.  Ventilation is the process of supplying fresh air to an enclosed space to refresh/remove/replace the existing atmosphere. Ventilation is commonly used to remove contaminants such as fumes, dusts or vapors and provide a healthy and safe working environment; in other words, it is an engineering control.  Types of Ventilation  Natural Ventilation- is a method of supplying fresh air to a building or room by means of passive forces, typically by wind speed or differences in pressure internally and externally.  Forced ventilation or mechanical ventilation -A type ventilation system that uses fans or blowers to provide fresh air to rooms when the forces of air pressure and gravity are not enough to circulate air through a compartment TYPES OF FORCED OR MECHANICAL VENTILATION:  Exhaust forced ventilation-an electrically operated exhaust fan at one end of a building and intake louvre at the opposite end.  Supply forced ventilation use a fan to pressurize compartments, forcing outside air into the compartments and pushing the air inside through ducts and vents.  Balanced forced ventilation if properly designed and installed, neither pressurize nor depressurize a system. Rather, they introduce and exhaust approximately equal quantities of fresh outside air and polluted inside air.  Energy recovery ventilation or Energy recovery ventilator (ERV) is a passive energy recovery device used to reduce the energy consumption of heating, ventilation and air-conditioning (HVAC) systems for conditioning the ventilation air.  Types of Refrigerant  Primary Refrigerants:  Primary refrigerants serve as the direct heat carriers in the refrigeration system and cool substances by absorbing latent heat. This category includes ammonia, carbon dioxide, sulphur dioxide, methyl chloride, methylene chloride, ethyl chloride, and the Freon group, among others.  Halo-carbon Compounds: This subcategory encompasses refrigerants containing chlorine and bromine, marketed under names like Freon, Genetron, Isotron, and Areton. These refrigerants, such as R10 (carbon tetrachloride), R11 (trichloromonofluoromethane), and R22 (monochlorodifluoromethane), find extensive use in domestic, commercial, and industrial applications due to their exceptional qualities.  Azeotropes: Azeotrope refrigerants consist of mixtures that cannot be separated into components by distillation. They maintain fixed thermodynamic properties and behave like simple substances. For instance, R-500 contains 73.8% R-12 and 26.2% R-152.  Types of Refrigerant  Hydrocarbons: This group features organic compounds used in commercial and industrial installations. Although they offer satisfactory thermodynamic properties, many are highly flammable. Key refrigerants in this category include R50 (methane), R170 (ethane), R290 (propane), R600 (butane), and R601 (pentane).  Inorganic Compounds: Before the prevalence of hydrocarbons, these refrigerants were widely used. Important members of this group are R717 (ammonia), R718 (water), R729 (air, a mixture of O2, N2, CO2), R744 (carbon dioxide), and R764 (sulphur dioxide).  Unsaturated Organic Compounds: This subcategory comprises refrigerants with ethylene or propylene as their constituents, including R1120 (trichloroethylene), R1130 (dichloroethylene), R1150 (ethylene), and R1270 (propylene).  Secondary Refrigerants:  Secondary refrigerants are substances that are initially cooled using primary refrigerants and are subsequently employed for cooling purposes. Examples include ice and solid carbon dioxide, which cool substances by absorbing their sensible heat.  https://testbook.com/mechanical-engineering/classification-of-refrigerants Coefficient of Performance  The cooling coefficient of performance of a system (refrigerator, air conditioning) is the ratio of heat out of the cold reservoir to the work put into the system.  https://energyeducation.ca/enc yclopedia/Coefficient_of_perfor mance Coefficient of Performance  The heating coefficient of performance of a system (heat pump) is the ratio of heat delivered to the hot reservoir to the work put into the system.  https://energyeducation.ca/enc yclopedia/Coefficient_of_perfor mance  Refrigeration Arrangement on Board  DIRECT EXPANSION SYSTEM  A direct expansion or DX cooling system is a type of air-conditioning system that removes heat from a space through evaporation and condensation of a refrigerant. The refrigerant absorbs the heat in the air, refrigerant is condensed back to a liquid by transferring the heat to outdoor air or water through a heat exchanger  Refrigeration Arrangement on Board  COLD BRINE GRIDS  Cooling of the cargo also depended on movement of air by natural convection, this type of chamber cooling required good, careful and ample dunnage of the cargo stowage. This appreciably diminished the amount of cargo that could be carried so that the system is no longer favored. Brine as a cooling medium (or secondary refrigerant) is cheap and easily regulated.  Refrigeration Arrangement on Board  Direct expansion batteries and air circulation This is a commonly used system (Figure 11.19) where the refrigerant circulates through batteries enclosed in trunks or casings. Air from the refrigerated chambers, is circulated through the batteries by fans. Its great advantages are economy in space, weight and cost, and the use of circulated air as the cooling medium or secondary refrigerant.  Refrigeration Arrangement on Board  Brine battery and air circulation This system, in which brine instead of primary refrigerant is circulated through the batteries, continued to be employed for reefer ships carrying such cargoes as chilled meat or bananas where extremely close control of temperature was required when direct systems were gaining favor elsewhere. Brine is relatively easy to regulate.  Air-Conditioning Arrangement on Board  Air conditioning arrangement on board:  Air-conditioning and ventilation-related conditions on ships have a considerable impact on the comfort of passengers, the well-being of the crew, and the efficient operation of equipment, systems, and installations, regardless of the type of ship.  The air conditioning plant is designed in principle to be self-contained within the fire zones or watertight compartments and to perform the following functions:  Supply cool air to the accommodation and wheelhouse.  Provide heating to the accommodation and wheelhouse air when necessary.  Remove excess moisture from the air or humidify it to a comfortable level if necessary.  Filter the air before it passes to the accommodation and wheelhouse.  Air-Conditioning Arrangement on Board  The air is supplied to the accommodation by an air handling unit (AHU), which is usually located inside accommodation block, in the air conditioning unit room. The unit consists of an electrically driven fan drawing air through the following sections starting from inlet to the outlet:  One air filter  One steam preheating unit  One enthalpy exchanger of the rotating composite type (Econovent)  One steam reheating unit  Two air cooler evaporator coils  Air-Conditioning Arrangement on Board  The exhaust section of the air handling unit comprises, from inlet to the outlet:  One return air filter  One exhaust ventilator  Automatic control for the humidification of the air is installed in the outlet portion of the AHU and the humidistat controller is positioned in the room housing the air handling unit. The humidifier nozzles are supplied with steam from the ship’s steam system.  https://chiefengineerlog.com/2022/05/22/vessel-accommodation-air-conditioning-plant- explained/  Mode of Heat Transfer  Conduction- Heat conduction (or thermal conduction) is the movement of heat from one object to another one that has different temperature when they are touching each other. For example, we can warm our hands by touching hot-water bottles.  Convection is heating transfer that occurs due to the motion of a fluid between a hot and a cold body. Free convection or natural convection is heating transfer that occurs due to fluid movement caused by buoyancy forces. Forced convection is heat transfer that occurs due to fluid flow.  Radiation thermal radiation, process by which energy, in the form of electromagnetic radiation, is emitted by a heated surface in all directions  Describe a Ventilation System for Accommodation Concepts and Types of Ventilation  Ventilation moves outdoor air into a compartment and distributes the air within the compartment.  The general purpose of ventilation in a compartment is to provide fresh and cool air. Three Basic Elements of Ventilation  Ventilation Rate — the amount of outdoor air that is provided into the space, and the quality of the outdoor air.  Airflow Direction — the overall airflow direction which should be from clean zones to dirty zones.  Air Distribution or Air Flow Pattern — the external air should be delivered to each part of the space in an efficient manner and the airborne pollutants generated in each part of the space should also be removed in an efficient manner.  Describe a Ventilation System for Accommodation Types of Ventilation Natural Ventilation  Natural forces (e.g. winds and thermal buoyancy force due to indoor and outdoor air density differences) drive outdoor air through purpose-built, building envelope openings.  Purpose-built openings include windows, doors, solar chimneys, wind towers and trickle ventilators.  This natural ventilation of buildings depends on climate, building design and human behavior.  Describe a Ventilation System for Accommodation Types of Ventilation  Mechanical Ventilation  Mechanical fans drive mechanical ventilation.  Fans can either be installed directly in windows or walls, or installed in air ducts for supplying air into, or exhausting air from a room.  Hybrid or Mixed-mode Ventilation  Hybrid (mixed mode) ventilation relies on natural driving forces to provide the desired (design) flow rate.  It uses mechanical ventilation when the natural ventilation flow rate is too low.  https://www.ncbi.nlm.nih.gov/books/NBK143277/  Describe a Mechanical Ventilation System for Ship’s Cargo Holds Two Types of Cargo Hold Ventilation  Natural Ventilation System  Natural ventilation relies on air circulation driven by convection, with outside air entering and inside air exiting the hold through vents located above the deck level.  Mechanical Ventilation System  Mechanical ventilation systems actively blow air across or through the cargo hold to remove hazardous gases or vapors.  If the cargo is prone to self-heating in the presence of moisture, mechanical ventilation should be applied in specific circumstances only.  In some situations, air-conditioning or specialized dehumidifying equipment should be used instead of ventilation to remove moisture from the atmosphere in the hold.  Where flammable gases might be present, the ventilation fans must be designed to avoid sparking and ignition or explosion.  https://www.marineinsight.com/marine-safety/why-is-cargo-ventilation-important-on-ships/  Describes the Construction and Operation of Fin Stabilizers What is a Fin Stabilizer?  A fin stabilizer is located under the water line on the side of a ship’s hull, providing a roll damping effect, to counteract a ship’s natural roll.  Many people never actually see a ship’s fin stabilizer until their vessel goes to the dry dock for surveys and hull inspections.  However, the onboard officers and engineers are expected to understand the way the system functions and know the individual components of their fin stabilizer system.  Describes the Construction and Operation of Flume Stabilizers  The Hoppe FLUME® Roll Damping System is a type of roll damping system individually sized for each specific application.  Number of tanks, proper dimensions, shape, location, internal structure and volume are varied to match each type of vessel and operating condition.  When correctly designed, the liquid flow within the tank will naturally lag behind the resonant roll motion of the ship by 90°.  This means the tank will create a stabilizing force directly opposing the forces created by the passing wave.  The FLUME® Stabilization System is a passive roll stabilizer. “Passive” due to the fact, that there are no moving parts necessary for its operation.  By a change in the liquid level, the natural response period of the tank is adjusted to correspond to the roll period of the ship.  The optimum stabilizing effect occurs when this liquid motion is 90° behind the motion of the ship. chrome-extension  //efaidnbmnnnibpcajpcglclefindmkaj/https://assets-global.website- Describes the Construction and Operation of Flume Stabilizers VIDEO  Air Conditioning  Stabilizer  https://www.youtube.com/  https://www.youtube.com/ watch?v=gVLhrLTF878 watch?v=A2QfV11XYD8