Prelab 2019 Refrigeration Lab Data Loop Efficiency & Effectivness

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Question Description

I need : Abstract, Result and Discussion and Conclusion for this report " prelab 2019"

u need to follow the objective on the report in order to know what to do. use my data "Refrigeration lab data r6" and compare it with with original data "refrigeration Data" using excel.

lab manual is provided. i provided an old report (_Refrigeration.pdf.) if that helps u but no copying from them at all ( i can add more) . i can provide some info and guidelines about abstract or results and discussion.

all figures and tables (e.g. t-test) from excel must be in the report in appendix section.

u might use the old reports but u may paraphrase.

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R2_Bandar Comparing the Coefficient of Performance for Varying Flowrates of Refrigerant through the Refrigeration System Group R2 Abdulaziz Fahad Giovanna Caruso Jason Ellis Written by: Bandar Alotibi 4/20/2017 R2_Bandar Abstract The process of refrigeration is an essential process in the industry. This process is accomplished by the use of a working fluid and mechanical energy to facilitate the transfer of heat from cold region to a hotter region. The process is affected by multiple parameters but in this paper of interest is the effect of the compressor setting and the refrigerant flow on the coefficient of performance (COP) of the refrigeration cycle. For this experiment the relationship between compressor speed and coefficient performance of the Armfield RA-1 MKII was determined. The performance of a refrigeration equipment can be determined using the coefficient of performance that relates the amount of heat transferred per unit of work added to the system. From the data gathered, maximum COP was achieved at 1% compressor setting with a value of 8.2 ยฑ 0.32 while the lowest at the 100% setting with a value of 4.8 ยฑ 0.38. It could be concluded that process is more efficient at low compressor settings with low refrigerant flow thus resulting in low effluent pressure. This is indicative of the overdesigned refrigeration cycle for the process simulated thus it could be used for a more intensive cooling process. . It was determined that with a 95% confidence level the sample means were not equal. Therefore, increasing the compressor speed had a significant effect on the coefficient of performance of the RA-1 MKII refrigeration unit. Introduction Refrigeration is the process of lowering the temperature of an enclosed space by forcefully removing the heat and transferring it elsewhere by means of a working fluid. Traditionally the process of refrigeration was made to occur naturally by means of temperature gradient where heat moved freely from an area of high temperature to an area of low temperature as applied in ice boxes [1]. Currently, refrigeration is accomplished by means of mechanical work which aids the transfer of heat through a cycle. The purpose of refrigeration is to create a low temperature zone in the space or object heat is absorbed [1]. The principle is applied in air conditioning equipment to provide the required cool environment in rooms for human comfort. The most popular use of refrigeration however is in preservation of perishables such as in homes, supermarkets and hotels. The goods are kept at low temperatures to discourage the growth of bacteria. In medicine, refrigeration is employed to provide very low temperatures for preservation of drugs and body R2_Bandar tissue samples. Most industrial cooling processes such as condensation of gases before storage and transportation and the cold treatment of materials also use the concept of refrigeration. The Objective of the experiment is to establish how refrigeration loop coefficient of performance is affected by varying the compressor speed, and to determine whether there is an optimum operation condition that would lead to the highest coefficient of performance. Theory Refrigerators are the heat transfer from a low temperature sink to a high temperature source. It uses refrigerant in cyclic devices to remove heat from the cold medium. The refrigeration cycle obeys the first law of thermodynamics. Such that energy can neither be created nor destroyed but it can only be transferred from one medium to another. ๐‘‘๐‘‘๐‘‘๐‘‘ = ๐›ฟ๐›ฟ๐›ฟ๐›ฟ + ๐›ฟ๐›ฟ๐›ฟ๐›ฟ (Equation 1) The maximum efficiency of a cycle and with less work used is the ideal case of the Carnot refrigeration cycle. The Carnot cycle consists of four processes: isentropic compression in a compressor, isobaric heat rejection in a condenser, throttling in an expansion device, and isobaric heat absorption in an evaporator. Since this process will not be reversible, an actual vaporcompression refrigeration cycle would be more likely to look at. The fluid friction and heat transfers to or from the surroundings are the biggest contributors to the process being irreversible. Both of these have effects on the entropy of the system. To find the efficiency of the refrigerator, the coefficient of performance (COP). The COP is the compares the desired output with the required input. It is always a positive number and can be greater than one. The purpose of the refrigerator is to remove heat from a cold space and release it into the surrounding [1]. COP can then be found by: ๐ถ๐ถ๐ถ๐ถ๐ถ๐ถ = ๐‘„๐‘„๐ฟ๐ฟ ๐‘Š๐‘Š๐‘–๐‘–๐‘–๐‘– (Equation 2) With ๐‘„๐‘„๐ฟ๐ฟ as the amount of heat absorbed from the water and ๐‘Š๐‘Š๐‘–๐‘–๐‘–๐‘– is the power used by the compressor. The ๐‘„๐‘„๐ฟ๐ฟ can be found by: R2_Bandar ๐‘„๐‘„๐ฟ๐ฟ = ๐‘š๐‘šฬ‡(โ„Ž1 โˆ’ โ„Ž4 ) (Equation 3) with the ๐‘š๐‘šฬ‡ is the mass flow rate of the liquid and โ„Ž1 and โ„Ž4 are the enthalpies corresponding to points 1 and 4, Figure 1. Figure 1: A pressure vs enthalpy diagram for a refrigeration cycle [2]. Methods Apparatus The unit used in the experiment was the RA1-MKII, which used a computer based interface to control the cycle. Below is a schematic of the unit and the locations of the sensors which were presented in the software. Along with Figure 2, Figure A1 illustrates the unit used for better understanding. R2_Bandar Figure 2: Schematic Diagram of the RA1-MKII Showing the places of the sensors with respect to the cycle [2]. Experimental Design The coefficients of performance were calculated using a refrigeration system described in the Armfield Refrigeration unit instruction manual for compressor speeds of 1, 50, and 100%. The experiment was repeated three times to compare the results statistically. The Armfield RA1-MKII software generated a table showing the COP and P2 as functions of time at intervals of 10 seconds for two minute. The COP values were then compared using statistical analysis at each speed explained in the methods of analysis. Two plots were generated: COP versus compressor speed and COP versus P2 to determine the effect that compressor speed and pressure have on the COP. Results and Discussion The obtained results are graphically presented in the succeeding figures in order to establish a trend for the relationship of the different variables such as the COP, compressor setting, refrigerant flow, and P2 (pressure). R2_Bandar From the data gathered in table 1 to table 6, it can been seen that the coefficient of performance is highly dependent on the refrigerant flow and subsequently the pressure of the effluent from the compressor. From Figure 3, an inverse relationship could be seen between the COP and the compressor setting thus a decrease in the COP is observed with an increase in the compressor setting. The declining trend is an indication that the compressor may be overdesigned for the process thus requires minimal setting of the compressor. A plot of COP against Compressor Setting 9.0 8.0 7.0 COP 6.0 5.0 4.0 3.0 2.0 1.0 0.0 0% 20% 40% 60% 80% 100% 120% Compressor Setting Figure 3: A graph of the coefficient of performance (COP) vs. compressor setting A similar trend is observed with the relationship of the COP with the refrigerant flow. The COP decreases with an increase in the refrigerant flow thus indicating that the process simulated actually requires minimal refrigerant for the set temperature. This similar trend is understandable given that the relationship between the two parameters which is shown in Figure 5. A direct relationship is established between the compressor setting and the refrigerant flow which is expected between the two parameters since the compressor drives the refrigerant (working fluid) into the system. R2_Bandar 9.0 8.0 7.0 COP 6.0 5.0 4.0 3.0 2.0 1.0 0.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 Refrigerant Flow (L/hr) Figure 4: A graph of the coefficient of performance (COP) vs. refrigerant flow 30.0 REfrigerant Flow (L/hr) 25.0 20.0 15.0 10.0 5.0 0.0 0% 20% 40% 60% 80% 100% 120% Compressor Setting Figure 5: A graph presenting the relationship between the refrigerant flow and the compressor setting. R2_Bandar 8.5 8.0 7.5 COP 7.0 6.5 6.0 5.5 5.0 4.5 4.0 6.0 6.5 7.0 7.5 8.0 P2 (bar) Figure 6: A graph of the relationship between the coefficient of performance (COP) and the pressure from the compressor to the condenser (P2) The relationship between the effluent pressure and the COP follows a similar decreasing trend sa with the refrigerant flow and the compressor setting. This is evident of the overdesigned refrigeration cycle for the process. T-tests were conducted among the trials and it can be concluded that the samples from the different compressor settings present different values and are not of the same sample population thus gives variance on the experimental set-up. This is backed up by the p-values from table 10 which are 0.000837 between the COPs at 1% and 50% and 0.012889 for the 50% and 100% trials. The trends observed between the different settings thus could be considered valid and varied enough to be conclusive. Conclusion The objective of the experiment was achieved since the relationship between the COP and coefficient performance of the Armfield RA-1 MKII was determined. The COP value achieved at 1% compressor setting had a value of 8.2 ยฑ 0.32 while the lowest achieved value was at 100% setting that had a value of 4.8 ยฑ 0.39. It could be concluded that process is more efficient at low compressor settings with low refrigerant flow thus resulting in low effluent pressure. This is indicative of the overdesigned refrigeration cycle for the process simulated. For better results to R2_Bandar be obtained, more time should be given to the compressor to allow it to settle before data is taken after each interval of measurements done. Besides, the data could be taken over longer periods of time. R2_Bandar References [1] Cengel, Yunus A., John M. Cimbala, and Robert H. Turner. Fundamentals of Thermalfluidsciences. New York: McGraw-Hill Higher Education, 2012. Print. [2] Armfield Ltd. Vapor-Compression Refrigeration Unit: Instruction Manual. Issue 2. August 2013. Print. RA1:MkII. Appendix Experimental Protocol 1. Verify the USB connection exists between the RA1-MK11 unit and the PC. 2. Check the RCD/combined circuit breaker is on - in the up position 3. Switch the unit on by flipping the power switch on the console. 4. Check to see what the temperature, pressure, and other values are; should be about ambient. 5. Set Pump 1 to desired speed and Pump 2 to desired speed. The condenser water pump (Pump 1) should be set to 40% and the evaporator water pump (Pump 2) should be 60%. 6. Verify water is flowing through the compressor and evaporator. Typically 1.5L/min and 5.5L/min respectively on the mimic diagram 7. Set the compressor motor speed to 10%, about 2000RPM, then click compressor on, on the screen. Allow system 30 seconds to reach 2000 RPM set point. Check the flowmeter F3 on RA1MK11 to ensure working fluid flows through the system 8. Set the sample options as โ€˜Automatic / 10 second intervalsโ€™ and click GO. The readings from the sensors will now be recorded. 9. While looking at the graphs of T1, T3, and T7 on the Y-axis and P1 & P2 on the secondary Y-axis, allow the system until the values are reasonably steady i.e. the changes within 5%. 10. Record the refrigerant flow rate on the variable area flowmeter F3 and enter the value on the mimic diagram. 11. Increase the compressor speed to 20% around 2460 RPM, and repeat steps 9 and 10. 12. Repeat this process for 40% (2945 RPM), 60% (3430 RPM), 80% (3915 RPM) and 100% (4400 RPM). 13. Set the compressor speed back to 50% and let the system reach dynamic equilibrium R2_Bandar 14. Click the โ€˜Stop buttonโ€™ to discontinue recording data and next click โ€˜Compressor onโ€™ to stop the compressor. Method of Analysis The null hypothesis for the experiment was that the Coefficient of Performance for 1, 50 and 100% compressor speeds respectively could be explained by random chance. Once all the data were obtained from the refrigeration unit, the optimum operation condition was be determined. The compressorโ€™s speed which lead to the highest COP was determined to be the optimum setting for the unit. Moreover, the set of COPs from the three trials at the same speed were compared statistically to another set at a different speed. This is to analyze the effect of compressor speed on the COP. Out of all the data, two plots were generated, COP versus compressor speed and COP versus the outlet pressure from the compressor (P2). Safety Safety precautionary measures and regulations must be observed to guarantee the safety of the users and the condition of the equipment. An immediate risk in this experiment setting is the presence of hot surfaces which can cause serious burns. It is recommended that users have to allow time for the equipment to cool before handling it. The โ€˜hot surfacesโ€™ labeled surfaces should never be touched or brought close to flammable materials. Since the equipment operates on an electrical supply, electrical safety measures have to be adhered to. The RA1-MKII should be operated with the prescribed frequency and voltage and it should be made certain that all the panels are in place before connection. The refrigeration unit is fitted with a Residual Current Device (RCD) which switches off electrical supply in case the system becomes electrically flawed. This device should be checked regularly and maintained in good working condition. The equipment contains rotating parts which demands special safety attention. It should be ensured that the protective guards against these parts are in place before operation. The users are required to clear off from the rotating parts when in operation and refrain from inserting any object past the protective guards. The parts must be left to come to rest after switching off the equipment R2_Bandar before attending to them. By fact that the equipment is heavy and hot, it should be maintained in a strong frame and handled carefully. The equipment should not be left to run unattended. Electrical safety - the Armfields RAI-MKII refrigeration unit should be operated on the specified voltage and frequency. The Residual Current Device (RCD) should be checked regularly to ensure that it is functioning well. The experiment involves the use of water and care should be taken for possible spillage. All electrical connections and adjacent devices should be secured to avoid water from reaching them. Raw data sheet. Figure A1: T-s phase diagram for the cycle [2]. R2_Bandar A. Raw Data Table 1: Raw data for Trail 1 at 1% compressor speed Table 2: Raw data for Trial 1 at 50% compressor setting Table 3: Raw data for Trial 1 at 100% compressor setting R2_Bandar Table 4: Raw data for Trial 2 at 1% compressor setting Table 5: Raw data for Trial 2 at 50% compression setting Table 6: Raw data for Trial 2 at 100% compression setting R2_Bandar Table 7: Raw data for Trial 3 at 1% compressor setting Table 8: Raw data for Trial 3 at 50% compressor setting Table 9: Raw data for Trial 3 at 100% compressor setting R2_Bandar B. T-tests Table 10: t-test comparing 1% and 50%compressor settings t-Test: Two-Sample Assuming Unequal Variances COP @ 1% 8.236167 0.102268 3 Mean Variance Observations Hypothesized Mean Difference df t Stat P(T<=t) one-tail t Critical one-tail P(T<=t) two-tail t Critical two-tail COP @50% 6.193722 0.051564 3 0 4 9.01959 0.000418 2.131847 0.000837 2.776445 Table 11: t-test comparing 50% and 100$ compressor settings t-Test: Two-Sample Assuming Unequal Variances COP @ 1% 8.236167 0.102268 3 Mean Variance Observations Hypothesized Mean Difference df t Stat P(T<=t) one-tail t Critical one-tail P(T<=t) two-tail t Critical two-tail COP @50% 6.193722 0.051564 3 0 4 9.01959 0.000418 2.131847 0.000837 2.776445 Statistical Equations Mean ยต ยต= ๐›ด๐›ด ๐‘ฅ๐‘ฅ ๐‘๐‘ ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ 4 R2_Bandar ยต is the sample mean, x is each data point, and N is the sample size. Standard Deviation ฯƒ N 1 ฯƒ = ๏ฟฝ ๏ฟฝ(๐‘ฅ๐‘ฅ๐‘–๐‘– โˆ’ ๐œ‡๐œ‡)2 N i=1 Equation 5 ยต is the sample mean, x is each data point, and N is the sample size. Variance ฯƒ2 N 1 ฯƒ = ๏ฟฝ(xi โˆ’ ยต)2 N 2 i=1 Equation 6 T-Test Pooled Standard Variation (๐‘›๐‘›1 โˆ’ 1)ฯƒ๐‘‹๐‘‹1 2 + (๐‘›๐‘›2 โˆ’ 1)ฯƒ๐‘‹๐‘‹2 2 ฯƒ๐‘๐‘ = ๏ฟฝ ๐‘›๐‘›1 + ๐‘›๐‘›2 โˆ’ 2 ฯƒ2๐‘‹๐‘‹1 is the variance of one of the samples. T-statistic ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ 7 R2_Bandar ๐‘ก๐‘ก = ๏ฟฝ๏ฟฝ๏ฟฝ ๏ฟฝ๏ฟฝ๏ฟฝ1 ๐‘‹๐‘‹1 โˆ’ ๐‘‹๐‘‹ 1 1 ฯƒ๐‘๐‘ ๏ฟฝ + ๐‘›๐‘› ๐‘›๐‘›1 2 ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ๐ธ 8 ๏ฟฝ๏ฟฝ๏ฟฝ ๐‘‹๐‘‹1 is the mean of population 1, ๏ฟฝ๏ฟฝ๏ฟฝ ๐‘‹๐‘‹2 is the mean of population 2 T-test: If the value is smaller than the critical t value the null hypothesis that the two sample means are equal is rejected. Troubleshooting an Armfield RA1-MKII Vapor Compression Refrigeration Unit Abstract: (Final Report) Introduction/Background: The vapor-compression refrigeration system (VCRS) is a system commonly used in buildings and cars which has the purpose of providing air conditioning. However, it is not limited to air conditioning, it can also be used in preservation or chilling of produce and goods in domestic or industrial use refrigerators. The VCRS is a system composed of four components, a compressor, a condenser, an expansion valve, and an evaporator. The system operates using a refrigerant which undergoes a repeatable cycle of phase changes, displacing hot air, and producing an air conditioning or cooling affect. The industries that most commonly utilize this method of refrigeration are oil refineries or natural gas processing plants, food production plants, and chemical processing plants. In oil refineries and natural gas processing plants, these types of refrigeration systems are used to condense product gases into a liquid form in order to transport the product more effectively. In food production plants refrigeration is used to provide the chiller with a place to displace heat in order to provide cold storage for products to extend the lifetime by inhibiting bacterial growth. Finally, refrigeration is used in chemical processing plants to control the humidity of processes as well as condense gases into liquids as needed (King). These types of refrigeration systems are often effective and reliable, however, with all systems, it is important to understand the unit operation in order to troubleshoot issues that occur with the equipment. By understanding the system, it becomes possible to recognize where maintenance is required. In industry, troubleshooting of VCRSs often begins with identifying the issue of the system. This often consists of examining the four main components of the system and running tests to identify which element of the system is producing the issue. Common issues with the system, include but are not limited to, the compressor not running, the fixed temperature being too high, having either a high or low discharge pressure, and having either a high or low suction pressure (King). Each of these issues can be addressed in different ways but correspond to the main components of the system which help to identify the problem. Objective: The objective of the experiment is to troubleshoot an Armfield Vapor-Compression Refrigeration Unit by collecting data by running the damaged refrigeration system and comparing it with previously obtained data of the same refrigeration system operating at normal operating conditions. Once the data is obtained, the system will be evaluated and repaired to operate at normal op ...
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