A Major Application Area Of Thermodynamics Engineering Essay

A Major Application Area Of Thermodynamics Engineering Essay A major application area of thermodynamics is refrigeration, which is the transfer of heat from lower temperature region to a higher temperature one. The devices that produce refrigeration are called refrigerators, and the cycles on which they operate are called refrigeration cycles. The most frequently used refrigeration cycle is a vapour-compression refrigeration cycle in which the refrigerant is vaporized and compressed alternatively and is compressed in the vapour phase. There are number of refrigerants which can be used in here, but the most commonly used on a commercial scale is a R12 (used in this experiment as well). The thermodynamics of ideal vapour compression cycle can be analyzed on a temperature versus entropy diagram as depicted in Figure 1. At point 1 in the diagram, the circulating refrigerant en- ters the compressor as a saturated vapour. From point 1 to point 2, the vapour is isentropically compressed (i.e., compressed at constant entropy) and exits the compressor as a superheated va- pour. From point 2 to point 3, the superheated vapour travels through part of the condenser which removes the superheat by cooling the vapour. Between point 3 and point 4, the vapour travels through the remainder of the condenser and is condensed into a saturated liquid. The condensation process occurs at essentially constant pressure. Between points 4 and 5, the saturated liquid refrigerant passes through the expansion valve (throttling device) and undergoes an abrupt decrease of pressure. This process results in the adia- batic flash evaporation and auto-refrigeration of a portion of the liquid (typically, less than half of the liquid flashes). The adiabatic flash evaporation process is isenthalpic (i.e., occurs at con- stant enthalpy). Figure 12 Temperature Entropy diagram 1 www. wikipedia.org/wiki/Refrigeration 2 http://upload.wikimedia.org/wikipedia/commons/f/f7/RefrigerationTS.png UMAR DARAZ Page 3 of 22 Thermodynamics Lab 2 Between points 5 and 1, the cold and partially vaporized refrigerant travels through the coil or tubes in the evaporator where it is totally vaporized by the warm air (from the space being refrigerated) that a fan circulates across the coil or tubes in the evaporator. The evaporator operates at essentially constant pressure. The resulting saturated refrigerant vapour returns to the compressor inlet at point 1 to complete the thermodynamic cycle. The area under the process curve on T-s diagram represents the heat transfer for internally reversible processes. The area under the process curve 5-1 represents the heat absorption in the evaporator, the area under the process 2- 4 represents the heat rejection in the condenser. In the ideal vapour compression refrigeration cycle all the heat losses and disruptions are being ignored, but in actual refrigeration cycle, we need to take these losses into consideration as they have been mentioned in this report later. The Hilton refrigeration laboratory unit R714 is capable of following entities;  · Investigation of the variation in refrigerator duty or cooling ability for various condens- ing temperature and the heat delivered to the cooling water with variation in condensing temperature. We can also investigate the variation in refrigeration coefficient of per- formance for the various condensing temperature.  · Investigation of the variation in coefficient of performance based on electrical, shaft and indicated power, determination of the overall heat transfer coefficient for the condenser cooling coil and performance of the thermostatic expansion valve.  · Investigation of the heat delivered to the cooling water with variation in condensing tem- perature, coefficient of performance as a heat pump for various condensing temperature, as well as power input based on electrical, shaft and indicated power. The important aspect of this report is to demonstrate the two laws of thermodynamics i.e. first and second law of thermodynamics. The first law is simply an expression of the conservation of energy principle, and it asserts that energy is thermodynamic property. Qout = Wnet + Qin Equation (1) In this experiment the Qin is provided by input voltage, this input is used to do the net work done on the refrigerant by compressor and motor, and the result of this produces the heat which is being removed by the condenser i.e. Qout. The second law of thermodynamics asserts that energy has quality and quantity, and actual processes occur in the direction of decreasing quality of energy. UMAR DARAZ Page 4 of 22 Thermodynamics Lab 2 Aims and objectives: The Hilton refrigeration laboratory unit R712 has been designed to allow students to fully investigate the performance of a vapour compression cycle under various conditions of evaporator load and condenser pressure. The main objectives of this laboratory are listed below;  · The demonstration of application of the First and second law of thermodynamics.  · The introduction of to refrigeration plant and calculate the various coefficient of perform- ance.  · Investigation of system losses, this includes motor, compressor, evaporator and con- denser losses. These losses (friction, heat losses) occur only in practical/commercial refrigerator, there are no losses in ideal vapour compressor refrigerator. UMAR DARAZ Page 5 of 22 Thermodynamics Lab 2 Apparatus The figure shown below looks like a refrigeration laboratory unit R712 (not exactly it) and it consists of the following components; Figure 23 Refrigeration laboratory unit Panel: High quality glass reinforced plastic on which the following components are mounted. Refrigerant: R12 Digital Thermometer: A device that measures temperature. Wattmeter: Allows measurement of the power input to either evaporator or motor. Voltage Controller: To vary evaporator load. Variable Area Flow meters: Variable area types to indicator R12 and H2O flow rates. Pressure Gauges: To indicate R12 pressure in evaporator and condenser. Spring Balance and Tachometer: These two together allow measurement of power required to drive the compressor. Expansion Valve: Thermostatically controlled type i.e. throttling device. Evaporator: Electrically heated device i.e. heat exchanger Compressor: (Internally mounted) Twin cylinder belt driven unit, along with spring balance force system. Condenser: A device or unit used to condense vapor into liquid. It is also called heat exchanger. Motor: A machine that converts electricity into a mechanical motion. 3 www.p-a-hilton.co.uk/English/Products/ Refrigeration__2_/refrigeration__2_.html UMAR DARAZ Page 6 of 22 Thermodynamics Lab 2 Procedure4 In prior performing an experiment the most important things to do are, to measure the atmos- pheric pressure, which would be added to the gauge pressure to get an absolute pressure for both condenser and evaporator, and to balance the two tips of the spring balance force, being applied on the compressor. In failure to do these things would cause a sufficient amount of error in the final results. In this experiment the condenser pressure is being kept constant i.e. 900KPa. Step-1 Turn on the refrigeration plant using one of the control breakers, and setting the evaporator voltage i.e. 40 100 volts, at the same time balancing the two tips of compressor load and set the condenser pressure to 900KPa, using rota-meter. Step-2 Record the following values; Evaporator Amps (1-2.42A), from wattmeter, compressor speed using tachometer, water and refrigerant flow rate using flow meter. Step-3 Record the spring balance force, reading directly from the scale. The hot water is in the tubes is indicated by red and cold water is indicated by blue sign in the refrigeration plant. Step-4 The flow rate is controlled by a throttling device (valve), the small changes in opening and closing the valve, effect the condenser pressure. Step-5 The temperature values of the refrigerant at different stages in the whole cycle at constant pressure is given by temperature dialler. Now we had all the values we needed, now we changed evaporator Amps value, recorded rest of the values as mentioned earlier and repeated the whole experiment for three to four times. The Refrigeration Laboratory Unit has three controls. Firstly a combined miniature circuit breaker and switch turns on both the compressor motor and the supply to the electrically heated evaporator. A combined variable area water flow meter and valve allow control of the condenser pressure and a panel mounted voltage controller allows control of the evaporator load from zero to full power. Refrigerant R12 vapour is drawn into the compressor from the evaporator mounted on the front of the panel. Work is done on the gas in the compressor and its pressure and temperature are raised. This hot, high pressure gas discharges from the compressor and flows into the panel mounted water cooled condenser, where heat is removed from it. This liquid then flows through a thermostatic expansion valve. Here it passes through a controlled orifice, which allows its pressure to fall from that of the condenser to that of the evaporator. The refrigerant has a satu- rated vapour phase at this point. The voltage across the heater elements may be varied from zero to that of the mains supply voltage by adjustment of a voltage controller situated on the front panel. Measurement of the power is carried out by a panel mounted digital wattmeter. 4 http://www.p-a-hilton.co.uk/R714-Edition-2-GREY.pdf UMAR DARAZ Page 7 of 22 Thermodynamics Lab 2 Results The observation table below shows all the values of different components in the refrigeration plant along with input indices and output indices, enthalpy of the cycle and losses in the system. The calculations required to get those results (to complete the table) are also listed after this table below. 1 Condenser pressure (gauge) Pc KNm-2 900 900 900 2 Evaporator pressure (gauge) Pe KNm-2 -20 20 40 3 Condenser pressure (Abs) Pc KNm-2 1001.663 1001.663 1001.663 4 Evaporator pressure (Abs) Pe KNm-2 81.663 121.663 141.663 5 Compressor suction t1 0 C -23.5 -22.6 -5.2 6 Compressor delivery t2 0 C 59.9 68.5 69.4 7 Liquid leaving condenser t3 0 C 31.6 34.8 33.8 8 Evaporator inlet t4 0 C -32 -23.6 -19.1 9 Water inlet t5 0 C 23.8 21.6 21.4 10 Water outlet t6 0 C 41.2 38.6 39.5 11 Water flow rate Mw g s-1 1.5 5.0 6.0 12 R 12 Flow rate Mr g s-1 0.7 1.5 1.9 13 Evaporator Volts Ve V 40 70 100 14 Evaporator Amps Ie I 1 A 1.70 A 2.42 A 15 Motor Volts Vm V 235 232 232 16 Motor Amps Im A 3.6 3.6 3.6 17 Spring balance Force F N 5.5 7.5 8.2 18 Compressor speed nc rpm 477 474 473 UMAR DARAZ Page 8 of 22 Thermodynamics Lab 2 19 Motor Speed = 3.17 ÃÆ'- nc Nm rpm 1512.09 1502.58 1449.71 20 h1 KJ/Kg 340 345 360 21 h2 KJ/Kg 385 400 420 22 h3 KJ/Kg 225 240 250 23 h4 KJ/Kg 160 170 180 24 Qe,Elec = Ve ÃÆ'- Ie W 40 119 242 25 Qe, R 12 = Mr(h1 h4) W 126 262.50 342 26 Wc = 0.0172ÃÆ'-FÃÆ'-Nm W 143.043 193.832 204.467 27 Power factor at shaft (power Wc) pf 0.43 0.48 0.52 28 Wm = Vm. Im. pf W 363.78 400.89 434.31 29 Wc = Mr (h2 h1) W 31.5 82.50 114.0 30 Q cond = Mr (h2 h3) W 112 240 323 31 Qw = Mw ÃÆ'- 4.18 (t6 t5) W 109.09 376.20 428.87 32 CoPnet = Qe, Elec / Wm 0.109 0.296 0.557 33 CoP R12 = (h1 h4)/(h2 h1) 4.0 3.1818 3.00 34 t41 can be found by (t1 t4) 0 C 8.5 1.00 13.9 35 CoP (te-t2) = t41 / (t2-t41) 0.165 0.015 0.250 36 Motor loss = Wc Wm W -220.73 -207.06 -229.84 37 Compressor loss = Wc-Wc W -111.54 -110.33 -90.47 38 System loss = Qcond Qw W 2.91 -136.20 -105.87 39 System loss = Qe, R12 Qe,Elec W 86 143.50 100.0 UMAR DARAZ Page 9 of 22 Thermodynamics Lab 2 Figure 3 A graph represents the relationship between net CoP and evaporator temperature Figure 4 A comparison of different losses of the system in one graph against Evaporator temperature The fluctuation and randomness in the graphs is because of the poor calibration and less number of repeated results (less tests provide less information), and most of the recorded results are based on guessed values. Calculations To find absolute pressure, we need an atmospheric and gauge pressure of the component. Now for two individual components,  · Condenser As we know Patm = à Ã‚ gh = 13600 kg/m3 ÃÆ'- 9.81 m/s2 ÃÆ'- 762 ÃÆ'-10-3m = 101.663ÃÆ'-103 Kg / ms2 = 101.663 KN/m2 Hence Pgauge,cond = 900 KN/m2 Pabs,cond = Patm + Pgauge,cond = 101.663 + 900 = 1001.663 KN/m2  · Evaporator As Patm = à Ã‚ gh = 13600 kg/m3 ÃÆ'- 9.81 m/s2 ÃÆ'- 762 ÃÆ'-10-3m = 101.663ÃÆ'-103 Kg / ms2 = 101.663 KN/m2 i. Pgauge,Evap = -20 KN/m2 Pabs,Evap = Patm + Pgauge,Evap Therefore = 101.663 + (-20)= 81.663 KN/m2 ii. Pgauge,Evap = 20 KN/m2 Pabs,Evap = Patm + Pgauge,Evap = 101.663 + (20)= 121.663 KN/m2 iii. Pgauge,Evap = 40 KN/m2 Pabs,Evap = Patm + Pgauge,Evap Therefore = 101.663 + 40 = 141.663 KN/m2 To find Qw (Heat removal from condenser) As we repeated the experiment three times, so water flow rate have three different values, hence we need to find Qw at three points, Qw = Mw ÃÆ'- 4.18 (t6 t5) When Mw = 1.5 gs-1, t6 = 41.2 0C, t5 = 23.8 0C Qw = 1.5 ÃÆ'-4.18 (41.2 23.8) = 109.098 W UMAR DARAZ Page 11 of 22 Thermodynamics Lab 2 As Qw = Mw ÃÆ'- 4.18 (t6 t5) When Mw = 5.0 gs-1, t6 = 39.6 0C, t5 = 21.6 0C So Qw = 5.0 ÃÆ'-4.18 (39.6 21.6) = 376.2 W Qw = Mw ÃÆ'- 4.18 (t6 t5) When Mw = 6.0 gs-1, t6 = 38.5 0C, t5 = 21.4 0C Qw = 6.0 ÃÆ'-4.18 (38.5 21.4) = 428.87 W To find Wc (work done by the compressor or a shaft loss) The work done by the compressor depends on spring balance force and motor speed, hence to get more work done out of the compressor we need to increase any of the above mentioned parameters. Therefore Wc = 0.0172ÃÆ'-FÃÆ'-Nm i. Wc = 0.0172ÃÆ'-5.5ÃÆ'-1512.09 = 143.043 W ii. Wc = 0.0172ÃÆ'-7.5ÃÆ'-1502.58 = 193.832 W iii. Wc = 0.0172ÃÆ'-8.2ÃÆ'-1449.71 = 204.467 W To find Wm (work done by the motor on a shaft to rotate) The work done by the motor is a product of voltage provided, amount of current flowing the motor and power factor of the shaft, which gives us the following values; Wm = Vm ÃÆ'- Im ÃÆ'- pf i. Wm = 235 ÃÆ'- 3.6 ÃÆ'- 0.43 = 363.78 ii. Wm = 232 ÃÆ'- 3.6 ÃÆ'- 0.48 = 400.89 iii. Wm = 232 ÃÆ'- 3.6 ÃÆ'- 0.52 = 434.31 UMAR DARAZ Page 12 of 22 Thermodynamics Lab 2 To find CoPnet (Total coefficient of performance of refrigerant) CoPnet = Qe, Elec / Wm By substituting different values of electric input heat energy (artificial input energy) and the work done by the motor, we get net coefficient of performance of the cycle, i. CoPnet = 40 / 363.78 = 0.109 = 11% ii. CoPnet = 119 / 400.89 = 0.296 = 30% iii. CoPnet = 242 / 434.31 = 0.557 = 56% To find CoP (te-t2) This is the coefficient of performance of ratio of temperature values at point 1-4 and difference of it, to the temperature of the refrigerant after compression, so we get following CoP (te-t2) = t41 / (t2-t41) i. CoP (te-t2) = 13.9 / (69.4 13.9) = 0.250 = 25% ii. CoP (te-t2) = 8.5 / (59.9 8.5) = 0.165 = 16% iii. CoP (te-t2) = 1.0 / (68.5 1.0) = 0.015 = 1.5% To find Qe, R 12(Heat removal from Evaporator) The given equation is à ¢Ã¢â€š ¬Ã‚ ¦ Qe, R 12 = Mr (h1 h4) By substituting different values of enthalpy, which we recorded from a pressure enthalpy diagram, so we get i. Qe, R 12 = 0.7 (340 160) = 126.0 ii. Qe, R 12 = 1.5 (345 170) = 262.5 iii. Qe, R 12 = 1.9 (360 180) = 342.0 UMAR DARAZ Page 13 of 22 Thermodynamics Lab 2 To find Wc (Input work done or compressor work loss) The input work done by the compressor can be calculated by finding flow rate of the refrigerant R12 and the difference of enthalpy of refrigerant before and after the compression. Wc = Mr (h2 h1) Substituting all three values of the above parameters (variables), we get i. Wc = 0.7 (385 340) = 31.5 ii. Wc = 1.5 (400 345) = 82.5 iii. Wc = 1.9 (420 360) = 114 To find Q cond (Heat loss by the condenser) Similarly heat loss by the condenser is a product of refrigerant flow rate to the difference of enthalpy values of it, before entering and leaving the condenser, we get Q cond = Mr (h2 h3) Now, using above stated equationà ¢Ã¢â€š ¬Ã‚ ¦ i. Q cond = 0.7 (385 225) = 112 ii. Q cond = 1.5 (400 240) = 240 iii. Q cond = 1.9 (420 250) = 323 To find CoPR12 (Coefficient of performance of refrigerant) CoP R12 = (h1 h4)/(h2 h1) Coefficient of performance of refrigerant is a ratio of all the enthalpy values in the cycle, here note that for ideal vapour compression refrigeration cycle h3 = h4 Hence we get i. CoP R12 = (340 160) / (385 340) = 4.00 ii. CoP R12 = (345 170) / (400 345) = 3.1818 iii. CoP R12 = (360 180) / (420 360) = 3.00 UMAR DARAZ Page 14 of 22 Thermodynamics Lab 2 Systems losses Motor loss = Wc Wm = 143.043 363.78 = -220.75 = 193.832 400.89 = -207.06 = 204.467 434.31 = -229.84 Compressor loss = Wc-Wc = 31.5 143.043 = -111.54 = 82.5 -193.832 = -110.33 = 114 204.467 = -90.47 System loss = Qcond Qw = 112 109.09 = 2.91 = 240 376.20 = -136.20 = 323 428.87 = -105.87 System loss = Qe, R12 Qe,Elec = 126 40 = 86.00 = 262.5 119 = 143.50 = 342 242 = 100.00 UMAR DARAZ Page 15 of 22 Thermodynamics Lab 2 Discussion of Results The observation table of results has been listed on page 8 9, and it is followed by all the calculations required to complete the table or to get the results. The experiment has been repeated three times, so all the results (values have been listed three times. In the calculation section the system losses and heat energy are shown as negative val- ues, its because the work is done on the system and heat is being removed from that particu- lar system, in this case its condenser. The positive values of system loss and heat energy shows that heat is being add in the system and work is done by the system, and in this case its evaporator. The condenser pressure i.e.900 KPa, was not exactly 900 KPa. As we were set- ting the pressure manually, so in the whole experiment the pressure was 900 KPa  ± 10%, it was because of the fluctuation in the gauge needle, so we assumed the considered pressure. The compressor pressure applied by spring balance force, affected the work done of the com- pressor on the refrigerant R12, because to get an accurate compressor work done, the two tips of the spring balance should be in balance (level), but during an experiment we were getting random values (results), so then I realised that something is wrong, so I looked at all the components of the refrigeration plant, and I found that the two tips of the spring were not bal- ance. Hence to get right results we had to redo the experiment. The throttling device or valve has a huge impact on condenser pressure, because by opening or closing i.e. changing a flow rate make a considerable amount of difference on condenser pressure and evaporator tem- perature. Motor loss refers to the consumption of electrical energy not converted to useful mechanical energy output, but in this case energy loss means less input energy to the compressor, which means a refrigerant would be less compressed by a compressor, so less heat would be re- moved by the condenser, and even after passing through the valve the refrigerant would still have a high temperature and pressure, hence less refrigeration would occur in a vapour com- pression cycle. Therefore we need to take into account power losses in the electric motor. In order to study this process more closely, refrigeration engineers use this pressure en- thalpy diagram shown in Figure 5. This diagram is a way of describing the liquid and gas phase of a substance. Enthalpy can be thought of as the quantity of heat in a given quantity, or mass of substance. The curved line is called the saturation curve and it defines the boundary of pure liquid and pure gas, or vapour. In the region marked vapour, its pure va- pour. In the region its marked liquid, it is a pure liquid. If the pressure rises so that we are considering a region above the top of the curve, there is no distinction between liquid and va- pour. Above this pressure the gas cannot be liquefied. This is called the Critical Pressure. In the region underneath the curve, there is a mixture of liquid and vapour. UMAR DARAZ Page 16 of 22 Thermodynamics Lab 2 3 2 4 1 Figure 65 Pressure Enthalpy diagram Evaporator Pressure line Condenser pressure line stage (Not a straight line) Isobar Condensation stage sion valve R12 Evaporation process 5 http://www.mvsengineering.com/chapter18.pdf UMAR DARAZ Page 17 of 22 Isentropic Compression R12 passing through Expan- Thermodynamics Lab 2 At the inlet of the compressor the temperature (t1) is the same as temperature of refrigerant R12 at the outlet of the evaporator. So we go straight from that temperature of left side of the doom (saturated liquid) to the right side of the doom (saturated vapour line), and then following the temperature gradient line, we go down and record the enthalpy value at that temperature and pressure. Similarly for the stage 2, we find h2 on x-axis. When the refrigerant leaves the condenser, it obtains a saturated liquid phase (left side of the doom), so taking the reference of condenser pressure line (red line), we take a straight line parallel to the y-axis, and wherever it meets the x-axis gives a value of enthalpy (h3) at stage three. In actual refrigerant plant, enthalpy at stage 3 and stage 4 is not same, but for the sake of calculation we assume that its an ideal condition and enthalpy at these two points is same. Test 1 As Compressor suction = t1 = -23.5 0C and condenser Pressure (Abs) = Pc = 1001.663 KNm-2 Hence the enthalpy h1 = 340 KJ/Kg Compressor delivery = t2 = 59.9 0C and Condenser Pressure (Abs) = Pc = 1001.663 KNm-2 Hence the enthalpy h2 = 385 KJ/Kg Here Liquid leaving condenser = t3 = 31.6 0C And Condenser Pressure (Abs) = Pc = 1001.663 KNm-2 Hence the enthalpy h3 = 225 KJ/Kg As mentioned earlier that h3 = h4 (Ideal condition) Hence the enthalpy h4 = 225 KJ/Kg But using temperature at evaporator inlet, t4 = -32 0C, we get Actual enthalpy value, h4 = 160 KJ/Kg Test 2 As Compressor suction = t1 = -22.6 0C and condenser Pressure (Abs) = Pc = 1001.663 KNm-2 Hence the enthalpy h1 = 345 KJ/Kg (from above p-h diagram) Compressor delivery = t2 = 68.5 0C and Condenser Pressure (Abs) = Pc = 1001.663 KNm-2 Hence using Figure 4, we get enthalpy h2 = 400 KJ/Kg Here Liquid leaving condenser = t3 = 34.8 0C And Condenser Pressure (Abs) = Pc = 1001.663 KNm-2 Hence the enthalpy h3 = 240 KJ/Kg UMAR DARAZ Page 18 of 22 Thermodynamics Lab 2 As mentioned earlier that h3 = h4 (Ideal condition) Hence the enthalpy h4 = 240 KJ/Kg But using temperature at evaporator inlet, t4 = -23.6 0C, we get Actual enthalpy value using figure 4, h4 = 170 KJ/Kg Test 3 As Compressor suction = t1 = -5.2 0C and condenser Pressure (Abs) = Pc = 1001.663 KNm-2 Hence the enthalpy h1 = 360 KJ/Kg Compressor delivery = t2 = 69.4 0C and Condenser Pressure (Abs) = Pc = 1001.663 KNm-2 Hence the enthalpy h2 = 420 KJ/Kg Here Liquid leaving condenser = t3 = 33.8 0C And Condenser Pressure (Abs) = Pc = 1001.663 KNm-2, Evaporator Pressure = 40 KPa Hence the enthalpy h3 = 250 KJ/Kg As mentioned earlier that h3 = h4 (Ideal condition) Hence the enthalpy h4 = 250 KJ/Kg But using temperature at evaporator inlet, t4 = -19.1 0C, we get Actual enthalpy value at this stage, h4 = 180 KJ/Kg 6However the expansion of the high pressure liquid, process 5 1 above is non reversible. Notice that Expansion is a constant enthalpy process. It is drawn as a vertical line on the P-h diagram. No heat is absorbed or rejected during this expansion, the liquid just passes through a valve, like water coming out of a tap. The difference is that because the liquid is saturated at the start of expansion by the end of the process it is partly vapour. Point 1 is inside the curve and not on the curve as described in the Evaporation process. At point 4 it starts to condense and this continues until point 5 when all the vapour has turned into liquid. Point 5 is saturated liquid. If more heat is removed, the liquid cools. It is then called sub-cooled liquid. Hence h4 is on a saturated liquid line (left side of the doom), and does not appear in a vapour compression cycle, and this is the case in all three tests. 6 http://www.alephzero.co.uk/ref/vapcom.htm#ph UMAR DARAZ Page 19 of 22 Thermodynamics Lab 2 As there is no moving part in the whole refrigeration plant apart from motor shaft of a compressor, so work done by them is zero, i.e. w = 0 So using steady state energy equation, we get W Q = h2 h1 Equation (2) As W =0, so equation (1) becomes Q = h2 h1 Or Q = h1 h2 Equation (3) The coefficient of performance or COP (sometimes CP), of a heat pump (i.e. refrigerator) is the ratio of the change in heat at the output (the heat reservoir of interest) to the supplied work.To find Cop value of refrigeration plant as well as for the refrigerant is a good practice, because this will illustrate that how much efficient of these two are. 7It takes a lot of heat to evaporate liquid. In other words a small amount of liquid circulating in a refrigerator can perform a large amount of cooling. This is one reason why the vapour compression cycle is widely used. The refrigeration system can be small and compact. Also from a practical point of view heat exchange is much better when using change of state evaporation and condensation. However the expansion of the high pressure liquid, process 5 1 above is non reversible. And so the efficiency of this cycle can never even approach Carnot efficiency. 7 http://www.alephzero.co.uk/ref/practcop.htm UMAR DARAZ Page 20 of 22 Thermodynamics Lab 2 Conclusion 8The vapour-compression cycle is used in most household refrigerators as well as in many large commercial and industrial refrigeration systems but the efficiency of this cycle can never even approach Carnot efficiency, because of its low coefficient of performance. In the refrigeration plant the operating parameters can be varied by adjustment of condenser cooling water flow and electrically heated evaporator supply voltage. Components have a low thermal mass resulting in immediate response to control variations and rapid stabilisation. Instrumentation includes all relevant temperatures, condenser pressure, evaporator pressure, refrigerant and cooling water flow rates, evaporator and motor power, motor torque and com- pressor speed. The most of components of refrigeration plant used in this experiment (R712) are manually calibrated scales (not digital), and based on this poor calibration all the recorded results are being guessed on the base of individual judgment, which is wrong most of the time. Anyway a small amount of liquid circulating in a refrigerator can perform a large amount of cooling. This is one reason why the vapour compression cycle is widely used. The enthalpy values which are being recorded directly from enthalpy pressure diagram (Figure 4), and based on how unclear that diagram is, I would say it is not a great source of information, but still we use this to find enthalpy. The system (refrigeration plant) has some losses, which have described earlier in this report, this includes motor loss, condenser and evaporator loss. In conclusion, I would like to say that by doing this experiment I learnt a great amount of knowledge, about refrigeration plant, and how it works, what kind of cycle more often use for this, how much efficient is this and how to calculate the different losses in this system. I would say by understanding the operation of this small scale refrigeration plant, I think I would be able to operate on an industrial scale refrigeration plant, because the basic principle is same. 8 http://www.alephzero.co.uk/ref/vapcomcyc.htm UMAR DARAZ Page 21 of 22 Thermodynamics Lab 2

Taste of Honey: From dependence to independence :: English Literature

Taste of Honey: From dependence to independence 'A Taste of Honey' was written by Shelagh Delaney when she was 18, and published in 1958. Four years later, in 1962, it was turned into a film. It shows life as it really was for many people in and around the slums of Salford, near Manchester, living with the poor housing and lack of opportunity. The characters are genuine; you can really believe in them. Some of the characters were totally different from the usual 'straight-laced' characters that were so common in the kitchen-sink dramas that were around at the time. For instance, a homosexual, a young pregnant unmarried girl, a semi-whore mother and a black sailor all living in the same areas, and some even living in the same houses as each other. This was completely different from the 'safe' plays of the time. There is hope in the play; the characters, especially Jo, are able to overcome their fears and problems and carry on with their lives. The characters in a taste of honey speak like typical working class people in the north of England. There are not many examples of regional dialect, but there are a few, such as when Helen says, 'Eee, there's a terrible draught,' showing that Helen is a resident of Lancashire. The characters drop letters, making them sound more common. There are many examples of this, including Jo saying, 'You packed 'em,' and Helen saying, 'Turn 'em all'. This shows that Helen and Jo are ordinary, common, working class or lower, people. The ancient Greeks believed that a play had to be realistic, and that to be realistic the action of the play should have one setting. The time the play took to act should be equal to the time covered in the plot and that the play should have only one main story. The Greeks called these ideas the 'three unties of time, action and place'. This is different to a taste of honey in that the play, although only having one main plot, has a sub-plot. The main story is the story of Jo, and the sub-plot being Helens story. There are many objects in the play which could contain a hidden meaning, from something a simple as darkness or a light bulb, to deeper things such as an eye patch or children singing. The list is endless. The very first instance of symbolism is the play's title, 'a taste of honey'. A taste is a very small amount for a short period of time. Honey is sweet, and therefore honey represents good. From Jo's point of view, her life is bad.

Gillette Essay

Case Analysis for Gillette: Product and Marketing Innovation 9/11/2012 Abstract Gillette is seeking means to retain dominance in market share they have lead for the last century. Along with sustaining market share Gillette has continued focus on expanding worldwide into less saturated markets. In this analysis multiple alternatives will be explored in order to make a recommendation on steps that would favor Gillette’s organization in meeting their aspirations. Situation Analysis Product quality and efficient marketing are the core value propositions that set the pace for Gillette’s success. With continued innovation in both product development and marketing strategies Gillette has been able to retain a commanding worldwide market share in a highly competitive, but mature, razor and blade market. Strong market share allowed Gillette to sustain profits even through economic droughts in recent years. On the flip side, Gillette’s innovation success also posed challenges. In order to maintain their market share, a dependency on continuous product improvement formed over time. Now Gillette will need to determine how to balance investment in research and development along with other areas of the organization. At times their own innovation of new product lines impacted their leading product lines in the market. During the 1990s Gillette found themselves cannibalizing their own successful products when trying to out due the competition. Even though internal competition shifted sales from one product line to another, Gillette’s sales were able to re-coop development costs. Expanding market share around the world also revealed challenges with varying religious and culture beliefs. Western influences have started to generate growth with European woman as younger generations watch American movies and television that depict women with sleek underarms and legs. Gillette’s latest innovation, the Fusion 5(+1) blade, was back in 2006. Since then Schick, Gillette’s leading competitor has not responded with their own break through. Gillette should be wondering what Schick might do next. Problem As the market Gillette has lead for so long became mature, their growth ultimately declined due to market saturation and increase competition. Fluctuations occurred only when newer, more innovative products were introduced. This put more pressure on development advancements and marketing tactics. Many analysts believe that Gillette and Schick, leaders in razors and blades, have reached the end of meaningful product innovation [1]. In 2006 when the Fusion 5(+1) blade was introduced, it exploded off the shelves. Gillette sold more than 4 billion Fusion razors with in the first two months. The Fusion’s initial success was quickly fleeting as sales reports showed that razors were outselling the cartridge refills. This was very concerning to Gillette as it is well-known that razor manufacturers earn most of their profits from refills, not the initial razor purchase. Critics also questioned why five blades were needed to get the best shave when Gillette had touted its three-bladed Mach3 as †the best a man can get. † â€Å"Consumer reports conclude that there were no additional performance benefits provided by the five-bladed Fusion, especially when compared to the Mach3† [1 pg391]. Economic recession also impacted sales as Gillette’s products went up in price due to a need to re-coop development costs. How can Gillette continue to maintain or grow market share in a mature market and keep future strategies aligned with customer wants? Alternatives Continue product line and marketing without major change. No additional research and development costs would need to be spent, which in return reduces the need to raise prices for maintaining their profit margin. However the risk looming would be competitor innovation impacting current market share. Schick may produce a new innovative product that would sway consumers from purchasing Gillette’s products. As stated in the case Gillette must find new ways to innovatively out-produce or out-market the competition. Investing in research and development to create new product line or enhance current products adds considerable expenses. Development costs will need to be re-cooped. This will keep competitors in check, but will be challenging to keep pricing competitive. Compliment current leading product lines that keep consumers happy. Promoting Christmas, Father’s day and Mother’s day gift grooming kits that meets more of the consumer’s needs will also introduce consumers to other product lines Gillette has to offer. Focus marketing potential growth opportunities globally by challenging resistance in product awareness and interests. As a Gillette razor consumer, I have encountered an inconvenience that I think can be solved and build customer loyalty. I’ve been using Mach 3 razors for over fifteen years, and when purchasing refills I have found it difficult to find blades that are compatible with the razor handle that I own. Thinking out of the box, what if Gillette were to make razor handles that are compatible with any of Gillette’s product line of refills? This would then provide consumers the freedom to purchase from a variety of Gillette’s product lines without having to spend extra money on a handle that works with the particular product refill. Owning a Gillette universal handle would also encourage customers to stay with Gillette refills as converting to another brand would cost more with the initial required handle purchase. Implementation From the case I would assume Gillette will continue to â€Å"innovatively out-produce or out-market the competition† [1]. I believe moving forward with developing a universal handle with Gillette refills would accomplish this. This would require investment into developing a new handle and rollout of the product. Here is an approximate timeline to complete.

What Can You Do with a Degree in Chemistry

Letter For Support For Recognizing My Husband, Frank R....

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The First Anti Semitic Act Essay - 1329 Words

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After WWI, Germany’s democracy started to fall part, losing their army, land, money, allies and Central Powers because Germany was forced to sign the Treaty of Versailles in 1919. This is when Hitler’s voice was a sign of hope for Germany and captured society’s fear. Since, Hitler blamed the Jewish people for losing World War I. Hitler was involved in the politics and tried to take control of the state government in 1923 with the Beer Hall Putsch. It was to going to make a new government in southern Germany to take out the Jewish race, creating racism (#2).Show MoreRelatedThe And Collective Anti Semitic Violence1679 Words   |  7 PagesCollective acts of violence during the late nineteenth century and early twentieth century became more prominent and apparent since the Civilizing Process meant that violenc e was no longer an inherent part of everyday life. 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Genetics and Mental Illnesses Essay Example For Students

Genetics and Mental Illnesses Essay Discoveries in genetics have helped change the way society looks at mental illnesses such as manic depression and schizophrenia. A generation ago, the leading theory about schizophrenia was that this devastating emotional and mental disorder was caused by cold and distant mothering, itself the result of the mothers unconscious wish that her child had never been born. A nation-wide lobbying effort was launched to combat such unfounded mother blaming, and 20 years later that artifact of the Freudian era is entirely discredited. Its widely accepted today that psychotic disorders are brain disorders, probably with genetic roots (Herbert 72). Just like every other topic in the genetics debates there are a few sides to the debate on the causes of mental disorders. One side feels mental illnesses are caused purely by genetic inheritance and another feels they are caused by environmental factors. A different side feels that it is a combination of the two. The problem is that most people take a side that supports either genetics or environment when most cases are not only genetic, but also environment. Take this situation for example. I have a thirteen year old friend who has been depressed a lot for the past few months, maybe even a year. Her mother recently decided to get her screened for depression. Well, they decided that she has a chemical imbalance in her brain that causes her to be depressed. In other words, shes depressed because genetically shes abnormal and that abnormality keeps her brain from making a certain chemical she needs to keep from being depressed. The thing is thats not the only reason shes depressed. Shes not very happy at home. Her parents wont let her do anything, which includes seeing her friends outside of school most of the time. They made her work all summer in her stepfathers shop and almost didnt let her quit when school started. Shes only allowed one phone call a day and it is limited to five to ten minutes. Now, as far as I am concerned, that is reason to be depressed. With circumstances like this, maybe her depression isnt all just the chemical imbalance caused by her genes, and maybe it has something to do with her environment. This situation illustrates the idea that mental illnesses are not only genetic, but are also environmentally caused. As Leonard Darwin says in The Need for Eugenic Reform, In studying cases of insanity both factors must always be taken into account, and the only logical course to adopt is to entirely discard all such phrases as due to heredity and due to environment. This does not mean that genetics does not sometimes cause the depression. For example, David Rosenthal summarized dozens of studies reporting that schizophrenia, a mental illness, clusters in families; that is, relatives of a schizophrenic are considerably more likely to become schizophrenic than are people without schizophrenic relatives (Stark 134). David G. Myers says at one point, Some people more than others seem genetically predisposed to particular fears and high anxiety. Identical twins often develop similar phobias, in some cases even when raised separately (Myers 464). Many studies have been done on the subject of twins who develop the same mental illnesses. In one study it was found that one pair of 35-year old identical female twins independently developed claustrophobia (Myers 464). Years of studies of families, adopted children, and twins separated at birth, suggest that both schizophrenia and manic-depressive illness run in families (Herbert 77). These problems become more prominent in instances where the afflicted person is an identical twin (Myers 464). This means that the closer you are genetically, the more likely you are to be schizophrenic also. The risk of having the gene is 10-15% if you have an affected sibling, but only 2-3% if your parent is the afflicted relative (Wilson). It has been proven that the 1-in-100 odds of any persons being diagnosed with schizophrenia become 1 in 10 among those with an afflicted sibling or parent, and close to 1 in 2 among those who have an afflicted twin (Myers 478). This is true whether the twins are reared together or apart (Myers 478). .ube5ed641f143698812fa5be138087d72 , .ube5ed641f143698812fa5be138087d72 .postImageUrl , .ube5ed641f143698812fa5be138087d72 .centered-text-area { min-height: 80px; position: relative; } .ube5ed641f143698812fa5be138087d72 , .ube5ed641f143698812fa5be138087d72:hover , .ube5ed641f143698812fa5be138087d72:visited , .ube5ed641f143698812fa5be138087d72:active { border:0!important; } .ube5ed641f143698812fa5be138087d72 .clearfix:after { content: ""; display: table; clear: both; } .ube5ed641f143698812fa5be138087d72 { display: block; transition: background-color 250ms; webkit-transition: background-color 250ms; width: 100%; opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #95A5A6; } .ube5ed641f143698812fa5be138087d72:active , .ube5ed641f143698812fa5be138087d72:hover { opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #2C3E50; } .ube5ed641f143698812fa5be138087d72 .centered-text-area { width: 100%; position: relative ; } .ube5ed641f143698812fa5be138087d72 .ctaText { border-bottom: 0 solid #fff; color: #2980B9; font-size: 16px; font-weight: bold; margin: 0; padding: 0; text-decoration: underline; } .ube5ed641f143698812fa5be138087d72 .postTitle { color: #FFFFFF; font-size: 16px; font-weight: 600; margin: 0; padding: 0; width: 100%; } .ube5ed641f143698812fa5be138087d72 .ctaButton { background-color: #7F8C8D!important; color: #2980B9; border: none; border-radius: 3px; box-shadow: none; font-size: 14px; font-weight: bold; line-height: 26px; moz-border-radius: 3px; text-align: center; text-decoration: none; text-shadow: none; width: 80px; min-height: 80px; background: url(https://artscolumbia.org/wp-content/plugins/intelly-related-posts/assets/images/simple-arrow.png)no-repeat; position: absolute; right: 0; top: 0; } .ube5ed641f143698812fa5be138087d72:hover .ctaButton { background-color: #34495E!important; } .ube5ed641f143698812fa5be138087d72 .centered-text { display: table; height: 80px; padding-left : 18px; top: 0; } .ube5ed641f143698812fa5be138087d72 .ube5ed641f143698812fa5be138087d72-content { display: table-cell; margin: 0; padding: 0; padding-right: 108px; position: relative; vertical-align: middle; width: 100%; } .ube5ed641f143698812fa5be138087d72:after { content: ""; display: block; clear: both; } READ: Elephantiasis I Did My Report On Filariasis, Which Is More Commonly Kn Essay Thus it is obvious that .