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Engineering Thermodynamics Assignment

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Added on  2021-06-18

Engineering Thermodynamics Assignment

   Added on 2021-06-18

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Running Head: Engineering Thermodynamics 1Engineering ThermodynamicsStudent’s nameUniversity affiliation
Engineering Thermodynamics Assignment_1
Engineering Thermodynamics21.Refrigerationa) Assuming a steady state operation for the refrigerator. The coefficient of performance for a freezer is given as COPref = QlWnetWhere Ql is the cooling effect energy and,W is the work input [ CITATION Enr12 \l 1033 ]. Therefore we can calculate for w by substituting given figures in above equation.Ql= 5kWCOPref = 1.3W=QlCOPref=51.3=3.8462kWThe refrigerator requires 3.8462kW to operate.b) Ql= 10,000kJ/h COPref =1.35the work input W=QlCOPref=100001.35=7,407.4074kJ/hConverting W to kJ/s 7,407.4074kJ3600=2.0576kJ/s but 1kJ/s=1kiloWatt Therefore the power required for the refrigerator to operate is 2.0576 kW.2. Heat pumpsA.i.COPhp=2.5 Qloss=60,000kJ/h 600003600=16.6667kW Qgenerated=4kW The temperature to be maintained Thot is 23 0C = (273+23) =300K Qh is the heat required to maintain the 230C Qh= Qloss – Q generated= 16.6667-4= 12.6667kW
Engineering Thermodynamics Assignment_2
Engineering Thermodynamics3 COPhp=QhW Therefore W=QhCOPhp=12.66672.5=5.06668kW The power input in the heat pump is 5.06668kW.ii.COPhp=ThotThot−Tcold = 300300−(273+1)=13.4545The best possible COP for the heat pump when the outside temperature is 10C is 13.4545.B.For an R-134 at 800kPa, the saturation temperature is 31.310C.Therefore, the working fluid at 400C is superheated. From the thermodynamics tables, the enthalpy of this fluid at400C h=276.45kJ/kg.Power consumed W= 1200W=1.2kWThe energy Qh = ṁ×h = 0.022kg/s × 276.45kJ/kg = 6.0819kJ/s Which is equal to 6.0819kW COPhp=QhW = 6.08191.2=5.06825The rate of heat absorption form the atmosphere Ql is Qh – WQl= 6.0819-1.2 =4.8819kW3. Carnot heat engine Energy in supplied Qh=700kJ at a temperature Th=500K Work input= -300kJ Sink temperature is 290 KFor a heat pump Qh= W + QlQl=Qh –W =700kJ- 300kJ=400kJFor a Carnot cycle Ql=TlS and,Qh=ThS Therefore QhQl=ThTl
Engineering Thermodynamics Assignment_3

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