File Name: marine refrigeration and air conditioning .zip
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Nicasio Mangosan Jay-r. Aditya Singh. Show More. No Downloads. Views Total views. Actions Shares. No notes for slide. Marine Refrigeration and Air Conditioning 1. Construction and Working of Ships Refrigeration plant: The refrigeration plants on merchant vessels play a vital part in carrying refrigerated cargo and provisions for the crew on board.
In reefer ships, the temperature of the perishable or temperature sensitive cargo such as food, chemical, or liquefied gas, is controlled by the refrigeration plant of the ship. The same plant or a smaller unit can be used for maintaining the temperature of different provision rooms carrying food stuffs for crew members. To avoid any damage to the cargo or perishable material so that the cargo in transported in good and healthy condition.
Refrigeration prevents growth of micro-organisms, oxidation, fermentation and drying out of cargo etc. Main Components of Refrigeration plants Main Components of Refrigeration plants Any refrigeration unit works with different components inline to each other in series. The main components are: 1. Compressor: Reciprocating single or two stage compressor is commonly used for compressing and supplying the refrigerant to the system.
Condenser: Shell and tube type condenser is used to cool down the refrigerant in the system. Receiver: The cooled refrigerant is supplied to the receiver, which is also used to drain out the refrigerant from the system for maintenance purpose. Drier: The drier connected in the system consists of silica gel to remove any moisture from the refrigerant Main Components of Refrigeration plants 5. Solenoids: Different solenoid valves are used to control the flow of refrigerant into the hold or room.
Master solenoid is provided in the main line and other solenoid is present in all individual cargo hold or rooms. Expansion valve: An Expansion valve regulates the refrigerants to maintain the correct hold or room temperature. Evaporator unit: The evaporator unit act as a heat exchanger to cool down the hold or room area by transferring heat to the refrigerant. Control unit: The control unit consist of different safety and operating circuits for safe operation of the refer plant.
Compressor safety devices The compressor is protected by three safety switches; 1. The OP switch or Oil Differential Pressure switch compares the measured lubricating oil pressure to the Suction crankcase pressure. Should the differential pressure fall below a pre-set minimum about 1. A time delay is built into the circuit to allow sufficient time for the lubricating oil pressure to build up when starting before arming the circuit.
The HP or High Pressure switch, is fitted to the outlet of the compressor before the isolating valve. On over pressurisation dependent on the refrigerant, up to about 24bar bar for R22 the switch will trip the compressor and a manual reset is required before restart. The LP or Low Pressure switch when activated at about 1 bar for R22 will trip the compressor and require a manual reset before the compressor can be restarted.
Compressor control devices This normally takes the form of an LP cut out pressure switch with automatic reset on pressure rise. The cut out set point is just above the LP trip point say at about 1.
An adjustable differential is set to about 1. The electrical circuit is so arranged that even when the switch has reset, if no room solenoid valves are open the compressor will not start. This is to prevent the compressor cycling due to a leaky solenoid valve. In addition to this extra LP switches may be fitted which operate between the extremes of the LP cut in and cut out to operate compressor unloaders.
Oil Separator It is situated on the compressor discharge line. The purpose of the oil seperator: - To return oil entrained in the gas, back to the compressor sump. The oil return may be float controlled as shown, electric solenoid controlled on a timer, or uncontrolled with a small bore capillary tube allowing continuous return.
With all of these methods a shut off valve is fitted between separator and compressor to allow for maintenance. The oil gas mix enters the separator where it is made to change direction, the heavier oil droplets tend to fall to the bottom. Filter Drier Can be either a compacted solid cartridge or bags of dessicant. The main purpose of this unit is to remove the moisture from the refrigerant.
Moisture cause two main problems: Firstly, it can freeze to ice in the evaporator and cause blockage. Secondly, it can form acids by reaction with the freon refrigerants. This acid attacks the copper in the lines and deposits its in other parts of the system. This can become particularly troublesome when it is deposited on the compressor mechanical seal faces leading to damage and leakage.
Fine particles which could possible block the expansion valve are removed. Thermostat and Solenoid Valve These two elements form the main temperature control of the cold rooms. The Thermostat is set to the desired temperature and given a 3 to 4 degree differential to prevent cycling. When the temperature in the room reaches the pre-set level the thermostat switch makes and the room solenoid is energised allowing gas to the refrigerant liquid to the expansion valve.
A manual overide switch is fitted as well as a relay operated isolating contact which shut the solenoid when the defrost system is in use. System Operation Assume that the rooms are all warm and the compressor is running with all the solenoid valves open supplying refrigerant to the respective expansion valve and evaporator.
Should one or two rooms be down to temperature the solenoids close thus reducing the volume of gas returning to the compressor. The suction pressure drops and the compressor unloads. If more rooms shut down then the suction pressure will drop to cut out point and the compressor will stop. When the rooms warm the solenoids open again, refrigerant passes back to the compressor, the suction pressure rises and compressor starts. With more rooms opening, the suction pressure increases and the compressor loads up more cylinders.
Thermostatic Expansion Valve TEV : Thermostatic expansion valve or TEV is one of the most commonly used throttling devices in the refrigerator and air conditioning systems. The thermostatic expansion valve is the automatic valve that maintains proper flow of the refrigerant in the evaporator as per the load inside the evaporator.
If the load inside the evaporator is higher it allows the increase in flow of the refrigerant and when the load reduces it allows the reduction in the flow of the refrigerant. This leads to highly efficient working of the compressor and the whole refrigeration and the air conditioning plant. Functions of the Thermostatic Expansion Valve The thermostatic expansion valve performs following functions: 1 Reduce the pressure of the refrigerant: The first and the foremost function of the thermostatic expansion valve is to reduce the pressure of the refrigerant from the condenser pressure to the evaporator pressure.
In the condenser the refrigerant is at very high pressure. The thermostatic expansion valve has an orifice due to which the pressure of the refrigerant passing through it drops down suddenly to the level of the evaporator pressure.
Due this the temperature of the refrigerant also drops down suddenly and it produces cooling effect inside the evaporator. At higher load the flow of the refrigerant is increased and at the lower loads the flow is reduced. The TEV constantly modulates the flow to maintain the superheat for which it has been adjusted. It allows the flow of the refrigerant to the evaporator as per the load on it.
This prevents the flooding of the liquid refrigerant to the compressor and efficient working of the evaporator and the compressor and the whole refrigeration plant. Defrost system Moisture freezes onto the evaporator eventually causing a restriction and reducing the efficiency of the plant.
This must be periodically removed.
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Psyctotherm as a ship repair company for refrigeration and air conditioning equipment. The company operates cooperatively with mr E. Psath- as and mr J.
Grasso Purger. Grasso Products b. Any data or other information in this brochure shall be deemed to be a general description of product properties and shall not be binding upon GEA. Binding product specifications may be agreed by GEA in bids, proposals, tenders or other offers issued in response to inquiries or calls for tenders or other invitations to bid.
The selfcontained cooling units are specially designed for marine application and are complete with compressor, condenser, evaporator and fan built together in a casing. All electrical wiring and refrigerant piping made. To be delivered with Rc and Ra as refrigerant. Designed as seawatercooled. The units can either be delivered for duct mounting or be equipped with plenum chamber accessory. The compressor is a welded type for 90MA and 90MA, serviceable hermetic type for 90MA and 90MA, and is equipped with suitable vibration isolators and filter drier.
Click Here To Download Now. One of the few machinery systems which need to run continuously on ships is its refrigeration plant. As a lifeline for all perishable food items and temperature-sensitive cargo, refrigeration plant is one of the most important systems on ships which requires utmost attention of engineers at all times. However, just like all other machinery on ships, the refrigeration system can also get into some trouble from time-to-time. Some of these problems are common but require immediate attention. When the compressor in the reefer circuit starts and suddenly stops, it can be because of the following reasons:. The most normal causes for such operation are:.
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