The noise of the heating, ventilation and air-conditioning(HVAC) system is the major factor affecting the cabin noise level. The acoustic performance tests have been carried out for the various sizes of the impedance composite muffler and the traditional dissipative muffler, in order to guide the design of the marine HVAC system and to reduce the noise level of the HVAC system. The results show that the basic noise reduction of the dissipative muffler can reach 15dB(A)/m. While for the impedance composite muffler with the twice external size of the dissipative muffler, its noise reduction performance is improved in the low frequency range. However, the A-weighted total noise reduction has not changed significantly for the impedance composite muffler. It can provide reference for the selection of the muffler and the design of the HVAC system.

The quality of ship food storage is directly related to the health of the crew. The preservation of fruit and vegetables, as a difficulty in the food storage, is an important factor affecting the self-sufficiency of the ship food. This paper introduces the principles and characteristics of the popular shipboard technologies for the preservation of fruit and vegetables at present. It also analyzes and discusses the application of the preservation technologies of fruit and vegetables on the different types of the military auxiliary ships from the practicability, economy and feasibility by combining with the characteristics of the food storage requirements for the various types of military auxiliary ships. It can provide reference for the design of the preservation of fruit and vegetables for military ships in the future.