Trekker's Hut on a Walking Track in the Australian Alps - Example

Technical report Prepared by --------- Month, Year Student Name Student Number 1 Introduction Alpine Trekking Pty Ltd has proposed to construct trekker’s hut at a specific site on a walking track in the Australian Alps. The trekker’s hut will be of a wooden A-frame supporting a steel roof with two side walls within the A-frame, one gable end has a door and a window and the other has a window only. The walls and internal ceiling of the hut are made from plywood. The trekker’s hut will have an electrical heating system and is seeking suitably qualified companies for the fundamental design. 2. Technical Analysis 2.1The design This crucial piece of infrastructure will accommodate a minimum of 12 adults sleeping on double bunks. Storage of equipment space will be a minimum floor area of 3m2 while cooking space is a minimum floor area of 2 m2. The diagram below of the proposed hut design. Figure 1:hut design There will be a head room of 0.8 m above the edge of the top bunk and access way of a minimum space of width 0.8 m on one side of each bunk to allow trekkers access or escape when emergencies. There are design Constraints to be met by qualified companies during tendering such as maximum height should be 4m while wall height should be 1.2m and roof angle is between 30 and 60 degrees. The trekker’s hut will have certain material Specifications due to climate conditions and construction should be consistent, providing designers with guidance as to whether the structure is thermally acceptable. 2.1Materials for hut Materials used will have a significant impact on energy conservation and keeping warm users of the hut. The following table is for materials used 2.2 Thermal transmittance rate There is need to determine Thermal transmittance rate of the hut that is the measure of thermal insulation of the construction’s external elements. This is the amount of heat energy (watts) transmitted through one m2 of construction for every oK temperature difference and is known as its U-value W/m2K. We begin by determining thermal Resistance “R” of a material (R) is calculated by dividing the thickness L (m) of the material by its Thermal Conductivity “λ”. R(m2K/W) = L (m)/λ (W/Mk) Plywood R(m2K/W) = = 0.1565 (m2K/W) Steel roofing R(m2K/W) = = 1.08 (m2K/W) Window glass R(m2K/W) = = 5.71 (m2K/W) Door plywood R(m2K/W) = = 0.313 (m2K/W) This is comparable to recommended thermal Resistance that is Walls 0.123 m2K/W, Floors or ceilings heat rising 0.104 m2K/W and Roofs Flat or Pitched 0.104 m2K/W After the thermal resistances, we will calculate the U-value which is the reciprocal of the sum of thermal resistances of the individual components that make up a hut. This thermal insulation value. Walls, doors and window and internal ceiling of the hut are made from plywood, therefore there U-value U=1/Rsi+R1+R2...Rn+Rso (m2W/K) U= = 2.105W/m2K It should be glass can reduce the U-value from 2.5 to 2.0 W/m2/K which is comparable with a more expensive triple glazed air gap panel 2.3 Heat loss The design of a hut will consider the heat loss which is measured in measured in watts. It is calculated using Area * U-value * temperature difference Where Area is area of the wall or window, temperature difference is the difference Minimum external temperature and desired internal temperature. The temperature difference will be obtained from environmental conditions as shown in the table below; Table 1: environmental condition Double bunks Wall (1.8x0.8)m2 * (1/0.1565) * (30)oK = 276.04watts Window= (1.2x0.6)m2 * (1/5.71) * (30)oK = 7,565.675watts Door = (1.8x0.8)m2 * (1/0.313) * (30)oK = 138.02watts Hut heat loss to air The portion near the hut is affected air heat flow which in may reduce or increase heat use in the hut. When a air flow enters a hut, a heat use is almost immediately changed to cold hot or cold but the since temperature is very cold then heat use inside increases. The core of the flow which is in viscid in relation to the walls is restricted from freely moving due to the growth of a viscous boundary layer. Therefore, it is important to ensure internal temperature and air movement are incorporated in the design as they influence the amount of heat that is used in the hut. Air movement can enhance spread of heat between bunks. Air flow can act as a cooling agent in the bunks, and it may help in the extinguishment of fire in the compartment. Heat transfer into air =V* *C*(TD–TL) Watts Where V is volume room, is density of air which is 1.514kg/m3, c specific heat value which is 1007.0 J/(kg*K) Cooking area Heat transfer into air =(2 x0.8)m3*1.514kg/m3*1007.0 J/(kg*K)*(314) = 766.034Kw per second or 212.78724722watt in one hour Movement area Heat transfer into air =(12 x0.8)m3*1.514kg/m3*1007.0 J/(kg*K)*(314) = 1276.72watt in one hour It is important to note that the density and specific heat of fluids change with temperature and it is important to adjust the flow rate and the specific heat to the actual temperatures. One may take additional readings of the temperature at the mid-point of a concentric hut but this is very difficult to achieve in other configurations and it is normal to take an average of the inlet and outlet temperatures for adjustment of the flow rate and the specific heat of the air. Heat demand Heat Loss from the hut will be obtained from summating the elemental losses and adding to the ventilation loss. This the heat demand with the hut Conclusion The hut will use plywood with thickness of 0.018m and thermal conductivity of 0.115W/ (m*K) for walls while doors will have thickness of 0.036m. The roof will be of steel with thickness of 0.0007m and thermal conductivity of 6.5W/ (m*K) and window glass will be with thickness of 0.008m and thermal conductivity of 1.4W/ (m*K). The wall will have thermal resistances of 0.1565 (m2K/W) while roof’s thermal resistances 1.08 (m2K/W). The Window and door will have thermal resistances of 5.71 (m2K/W) and 0.313 (m2K/W) respectively. Heat loss through wall Double bunks 276.04watts while from wind is 7,565.675watts and door is 138.02watts. There is loss of heat through air. Loss in the Cooking area is 212.78724722watt in one hour and movement area is 1276.72watt in one hour . References IEE wiring regulations. Simple Assessment of Electrical Demand- all electrical Installations Have To Comply With the “Electricity At Work Act 1989”. Incropera, F.P. and DeWitt, D.P., 2002. Fundamentals of Heat and Mass Transfer, 4th Edition, John Wiley & Sons, N.Y Incropera, P. & Dewitt, D., 2006. Fundamentals of heat and mass transfer. New York: John Wiley & Sons Shi, X, Kong, H., Li, P., Uher, C., Yang, J., Salvador, J. R., Wang, H., Chen, L., & . Zhang, W., 2008. Low thermal conductivity and high thermoelectric figure of merit in n-type Bax YbyCo4Sb12 double-filled skutterudites Walker, S. (2007). Sustainable Design. 2nd ed. USA: EarthScan. p15-23. Read More