Air conditioning, ventilation, and compressed air

46 CFR §58.16-20

§ 58.16-20 -20 Ventilation of compartments containing gas-consuming appliances. (a) Compartments containing gas-consuming appliances which are located above the weather deck must be fitted with at least two natural ventilator ducts led from the atmosphere with one extending to the floor level and the other extending to the overhead of the compartment. Powered ventilation may be used provided the motor is outside the compartment. (b) Compartments in which gas-consuming appliances are located entirely below the weather deck must be provided with powered ventilation of sufficient capacity to effect a change of air at least once every 6 minutes. The motor for the powered ventilation must be located outside the compartment.

46 CFR §58.20-1

§ 58.20-1 -1 Scope. (a) The regulations in this subpart apply to fixed refrigeration systems for air conditioning, refrigerated spaces, cargo spaces, and reliquefaction of low temperature cargo installed on vessels. (b) The regulations in this subpart do not apply to small self-contained units.

NAVEDTRA 14075 §6-1

NAVEDTRA 14075 §6-1 — The vapor-compression refrigeration cycle Refrigeration moves heat from a cold space to a warmer one, against its natural direction, by repeatedly evaporating and condensing a refrigerant in a closed cycle. It works because a liquid absorbs a large amount of heat (its latent heat) when it boils, and gives that heat up again when it condenses; by controlling the pressure, the refrigerant can be made to boil at a low temperature in the space being cooled and to condense at a higher temperature where the heat is rejected. The vapor-compression cycle has four essential components connected in a loop: the compressor, the condenser, the metering (expansion) device, and the evaporator. Following the refrigerant around the loop: low-pressure liquid refrigerant boils in the e…

NAVEDTRA 14075 §6-2

NAVEDTRA 14075 §6-2 — Compressors The compressor is the heart of the refrigeration system: it draws low-pressure vapor from the evaporator, compresses it to a pressure high enough that the refrigerant will condense at the available cooling-water or air temperature, and so keeps the refrigerant circulating and the heat moving. Most marine refrigeration and air-conditioning plants use reciprocating compressors, in which pistons draw vapor in through suction (reed) valves on the down-stroke and force it out through discharge valves on the up-stroke; they may be open (driven by an external motor through a coupling or belt, with a shaft seal) or hermetic/semi-hermetic (motor and compressor sealed in one housing). Larger air-conditioning plants often use rotary screw or centrifugal compressors,…

NAVEDTRA 14075 §6-5

NAVEDTRA 14075 §6-5 — Evaporators and cooling coils The evaporator is where the refrigeration system does its useful work: low-pressure liquid refrigerant boils inside the evaporator coil and absorbs heat from the air, water, or brine around it, cooling the refrigerated space or product. Because the refrigerant is boiling at low pressure and therefore low temperature, heat flows into it from the warmer surroundings; the refrigerant leaves the evaporator as a low-pressure vapor, slightly superheated, on its way to the compressor suction. Evaporators are built in two general arrangements. In a dry-expansion evaporator the metering device feeds just enough refrigerant that it is fully evaporated by the coil outlet; in a flooded evaporator the coil is kept filled with liquid to a level set by…

NAVEDTRA 14075 §6-7

NAVEDTRA 14075 §6-7 — Air conditioning systems and controls Shipboard air conditioning uses the same vapor-compression refrigeration cycle to cool and dehumidify air for crew comfort and for equipment spaces. In a typical central plant, refrigerant chills either the air directly (a direct-expansion coil in an air handler) or a supply of chilled water that is then pumped to cooling coils throughout the ship (a chilled-water system, favored on larger vessels because it distributes cooling with water piping rather than long refrigerant lines). Air handlers draw in a mixture of recirculated and fresh outside air, pass it across the cooling coil where it is cooled and dehumidified, and distribute it through ducts to the spaces; the moisture condensed out of the air on the coil is collected and…