| A square cabin can provide a shelter for the field work personnel.A transformable cabin may increase the available space for the personnel and improve the living quality of the personnel.To improve the energy efficiency and adapt to the application environment,the rigid envelope of a transformable cabin should have some characteristics,such as good mechanical properties,light weight and high thermal insulation performance.The environmental control system of the cabin can provide comfortable temperature,air velocity and fresh air supply for the personnel indoor,protecting them from the extreme weathers or oxygen-poor environment in the field and insuring a more comfortable environment to live and work.The thermal control system of the square cabin puts forward a high requirement for the insulation performance of the cabin envelope structure.A kind of lightweight insulation composite,which can combine the super insulation of state-of-the-art insulation materials or structures and the machinability or adaptability of traditional insulation materials,was proposed as the cabin envelope.The composite consists of two components,i.e.,polyurethane(PU)foam as the base material and vacuum insulation panel(VIP)or silica aerogel as the core material.The core material is in plate shape and covered with the base material on all sides.The thermal conductivity of the core material is nearly one order lower than that of the base material.The effective thermal conductivity of the insulation composite was explored by simulation.The simulation results show that the effective thermal conductivity of the composite increases with the increase of the thermal conductivity of the core material.The effective thermal conductivities of the composites decrease with the increase of the cross-section area of the core material perpendicular to heat flow direction and the thicknesses of the core material parallel with heat flow direction.These rules can be elucidated by a series-parallel mode thermal resistance network method.For composite with a VIP as the core material,when the cross-section area and thickness of the VIP are respectively larger than 60%and 21%of the composite,the composite's effective thermal conductivity can be 50%or less than that of the base material.The areal density of the composite increases with the increase of the core material size.The effective thermal conductivities of PU foam plate,VIPs and composites were measured by a steady-state method,and it was confirmed that the measurement deviation of the thermal conductivity of VIP was caused by the thermal bridge effect around.The insulation performance of the cabin adopting the composites were simulated to determine the influence of the core material type and the cabin frames.The heat loss from the envelope adopting the insulation composites with VIP or aerogel as the core material is reduced by 44.5%or 22.7%respectively,compared with that from the envelope adopting traditional insulation materials.For the envelope adopting the insulation composites with VIP as the core material,when the frame area accounts for 6%of the internal wall area,the heat loss through the frames accounts for approximately 50%of the overall heat loss.To provide a proper temperature and sufficient cooling power for the square cabin,an ice storage air conditioning system is necessary.The performance of the air conditioning system is restricted by the cooling power of the ice storage system directly.We proposed a compact and expandable high-power phase-change cooling system with parallel coil-plate heat exchanger units,with ice as the cool storage medium and ethylene glycol solution as the refrigerant carrier.In order to evaluate the cooling effect of the system,a simulation model of the coil-plate heat exchanger unit was established for the ice-melting and cool-discharging process,and was verified by a system experiment.Analogous to the solar flat-plate collectors,the influences of the structure parameters of the tube-plate unit on the cooling power were discussed.The comprehensive influences of the tube pitch and plate spacing on the cooling power and time were analyzed.The influences of the spacing and the inlet condition of the coil-plate unit on the cooling power were also discussed.When the plate spacing is large enough,the cooling power at any time is independent of the plate spacing.It is found that the main coolant factor affecting the cooling power is its inlet temperature,rather than the flow rate.Experimental and simulation results show that the minimum value of the cooling power density of a single coil-plate heat exchanger unit is 2.69 kW/m~2,and its mean value is approximately 4.10 kW/m~2 during the first 1200 s.During the first 7200 s,the the cooling power density is 0.22 kW/m~2,and its mean value is approximately 1.49 kW/m~2A square cabin can provide a large available space including the core module and extended modules for diverse demands such as dining or sleeping.The aiflew organizations in the transformable cabin were simulated by computational fluid dynamics and thermal solution techniques.The air supply duct on the ceiling of the cabin was designed to uniform the supplying air quantity through each outlet by adding baffles in the duct.Baffles can also make the export winds nearly perpendicular to the duct wall.The indoor airflow velocity and temperature fields in the condition of people gathering for dinner were obtained by simulation,so as that in the condition of people scattering for sleeping.In the dining condition,the barriers to the uniform airflow and temperature are the crowd occupying the core module.In the sleeping condition,the dominating barriers are the walls between different modules.The airflows were uniformed between different modules by setting ventilation apertures across the partitions.The simulated results of transient condition show that the temperature distribution in the cabin forms in the first 15 minutes because of the strong air supply condition and the negligible effect of the external environment. |
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