Views:25 Author:Site Editor Publish Time: 2020-10-16 Origin:Site
Marine air conditioner
Ships sail in various sea areas, with complex weather conditions and changing climates. In order to enable crews and passengers to have a comfortable living and working environment, air conditioning technology can be used to create a suitable artificial climate in the cabin and improve the environment.
Requirements for marine air conditioning
Ship air conditioning is only used to meet the needs of health and comfort, and to create a good working and rest environment for the crew. It is called comfort air conditioning. It is not very strict with the air conditions, and generally should meet the following aspects.
①Air temperature: 19~22℃ in winter, 24~28℃ in summer, indoor and outdoor temperature difference no more than 3~5℃, and summer indoor and outdoor temperature difference no more than 6~10℃.
②Air humidity: relative humidity in winter: 30%~40%, relative humidity in summer: 40%~50%.
③Air freshness degree: It includes two requirements of fresh air (less dust and harmful gases) and freshness (sufficient oxygen content) to meet the needs of human breathing for oxygen. The fresh air supply is only 2.4m³/h per person. To reduce harmful gases such as carbon dioxide and flue gas below the allowable value, the fresh air volume is required to be 30-50m³/h per person.
④Air velocity: In the cabin, the air has a slight flow, which makes people feel not stuffy. The air velocity should be 0.15~0.20m/s, and the maximum should not exceed 0.35m/s, otherwise people will feel uncomfortable.
⑤Noise: The measured noise should not exceed 55-60dB(A) from the air outlet of the indoor air conditioner.
Thermal load and wet load of cabin
The heat that penetrates into the cabin per unit time and causes a change in room temperature is called the sensible heat load of the cabin, which mainly includes:
① Infiltration heat: The heat transmitted through the ship's enclosure in summer accounts for about 26%-31% of the cabin's sensible heat load.
②Solar radiant heat: about 25%-27% penetrates through the external window.
③The heat dissipation of the human body: the average person is about 210kJ/h, and the heat dissipation of the human body accounts for about 16%-18%.
④Lighting and other electrical equipment heat dissipation: about 4%-5%.
⑤ Heat dissipation of food, combustion or other processes:
Use Q for sensible heat load. (kJ/h) means that in summer, the heat generated by solar radiation and the infiltration heat generated by the temperature difference between indoor and outdoor environment are transferred from the outside to the inside, and the sensible heat load is positive. In winter, the temperature difference between indoor and outdoor causes heat to radiate from the inside to the outside. Although the transmission direction of the sun’s radiation and the heat from the human body and equipment does not change, its value is small compared with the previous item. In general, the winter cabin is Heat seeping from the inside to the outside, the sensible heat load is negative.
The humidity of the air-conditioned cabin comes from the water vapor emitted by the human body, food and water, and the humidity caused by the air intrusion. The amount of water vapor emitted per hour is called the humidity load in the cabin, and F is used. (g/h) said. The human body and food always emit water vapor to increase the humidity in the cabin, so the humidity load in the cabin is always positive regardless of winter and summer.
To achieve the heat and humidity balance of the empty cabin, it is required that when the air-conditioning cabin is stable, the heat brought by the air supply and ventilation of the air-conditioning and the sensible heat load and the humidity load in the cabin are balanced.