PERFORMANCE EVALUATION OF TWO STAGE AIR COOLER IN DIFFERENT SPEED

International Journal of Mechanical Engineering and Technology (IJMET) Volume 7, Issue 3, May June 2016, pp.329 341, Article ID: IJMET_07_03_030 Available online at http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=7&itype=3 Journal Impact Factor (2016): 9.2286 (Calculated by GISI) www.jifactor.com ISSN Print: 0976-6340 and ISSN Online: 0976-6359 IAEME Publication PERFORMANCE EVALUATION OF TWO STAGE AIR COOLER IN DIFFERENT SPEED MOHAMMAD UL HASSAN Department of Mechanical Engineering, NIT Patna, India ABSTRACT During summer use of khush curtains and water spraid over the khash (fibre) curtain for air cooling is done. But the determination of the extent of cooling is limited up to the wet bulb temperature in Conventional Cooler air is passes at uniform rate through wetted pad. In this process humidity increases sometimes which is not desirable. In Two Stage Air Cooler the primary air is cooled by a contact surface which is maintained at lower temperature air and water on the other side of the contact surface After analysis it is found that in Two Stage Air Cooler Effective temperature decreases COP increases up to 13 which are significantly higher than normal and conventional air conditioner. Refrigeration effect increases. Makeup water recharges time increases for the same configuration has been obtained for it is 24 hours 54 minutes and for conventional it is 15 hours 2 minutes. In two stage air with cover noise has been drastically reduce by the increase damping effect of covers Specific humidity increase is significantly lower than that of in case of Conventional Cooler. On the basis analysis it is recommended that two stage indirect air is energy effective, eco friendly, cost effective cooling system and with some further modification it may be hope as replacement of air conditioner. In direct expected limit lower temperature was 22.6 where as experimentally the temperature attains are 24. In indirect system the expected temp was 20.5 where as the actual temperature attain is 21.9 less than the wet bulb temperature with lesser relative humidity than 100%) Key words: Conventional Air Cooler, DBT, Heat Exchanger, Primary Pump, Two Stage Air Cooler WBT Cite this Article: Mohammad Ul Hassan, Performance Evaluation of Two Stage Air Cooler In Different. International Journal of Mechanical Engineering and Technology, 7(3), 2016, pp. 329 341. http://www.iaeme.com/currentissue.asp?jtype=ijmet&vtype=7&itype=3 http://www.iaeme.com/ijmet/index.asp 329 editor@iaeme.com

Mohammad Ul Hassan INTRODUCTION Principle of evaporative cooling has been used since long back, during summer use of khush (fibre) curtains and water sprayed over it for air cooling. Other example of evaporative cooling are use of shurahi pot for water cooling, cooling tower, spray ponds etc. But the determination of the extent of cooling is limited up to the wet bulb temperature. In Conventional Cooler air is passes at uniform rate through wetted pad. In this process humidity increases sometimes which is not desirable. In Two Stage Air Cooler the primary air is cooled by a contact surface which is maintained at lower than temperature of incoming atmospheric air. In both the process minimum temperature can be achieved theoretically is wet bulb temperature (WBT) of the incoming air. PROPOSED MODIFICATION The temperature of air decreases from i to o in Conventional Cooler. in indirect evaporative the temperature of i 1 is lower than temperature at i and if proceeding is done on the constant WBT Line then it goes up to O 1 which is lower than the previous O. This indicates that if temperature of air at i is cooled to i 1 prior to entry to main by any means lower temperature can be achieved. This suggests need of cooling of air prior or in other words two stages cooling. The equipment based on this principle is designated as Two Stage Air Cooler and theoretically one may reach up to the dew point temperature. EXPERIMENTAL SETUP The heat exchanger is fitted on the back panel of the, the inlet is connected with the secondary pump situated inside the tank so that water supply from for the exchanger is from the tank and outlet is connected with a pipe to discharge the water in the same tank connected http://www.iaeme.com/ijmet/index.asp 330 editor@iaeme.com

Performance Evaluation of Two Stage Air Cooler In Different For measurement of temperature of cold water entering the heat exchanger a thermometer probe is inserted in the inlet pipe and for measurement of hot water temperature coming out of the heat exchanger a thermometer probe is inserted in the outlet pipe. For measurement of air temperature at the inlet of heat exchange, outlet of heat exchanger, outlet of and ambient temperature four thermometers installed at respective position. Also for the measurement of energy consumption at different arrangement that is combined direct and indirect and direct only at various speed/velocity energy meter was installed to get energy consumption in kwh. Nomenclature DBT = Dry bulb temperature WBT = Wet bulb temperature A 1 = area of inlet of A 3 = area of outlet of T 1 dbt = dry bulb temperature of air inlet to heat exchanger T 2 dbt = dry bulb temperature of air after passing through heat exchanger http://www.iaeme.com/ijmet/index.asp 331 editor@iaeme.com

Mohammad Ul Hassan T 3 dbt = dry bulb temperature at outlet of T 1wbt = wet bulb temperature at inlet of heat exchanger T 3wbt = wet bulb temperature at outlet of RH 1 = Relative humidity at inlet to heat exchanger RH 3 = Relative humidity at outlet of W 1 = specific humidity at inlet of heat exchanger W 3 = specific humidity at outlet of h 1 = specific enthalpy at inlet to heat exchanger h 3 = specific enthalpy at outlet T w1 = Inlet temperature of water T w2 = Outlet temperature of wate S w = specific heat of water S a = specific heat of air DATA COLLECTION AND CALCULATION Data was collected on various days on different time. All the parameter required for calculation and performance evaluation of two stage air needed has been arranged in tabular form for convenience in visualisation and graph plotting. Calculation of Velocity Velocity was calculated at five different points then average of them is taken for both inlet and outlet for high speed, medium speed and low speed respectively. The velocity of air may vary for different atmospheric conditions Points Table 1 Velocity at inlet of at different points in different speed Side Inlet Outlet High speed (m/s) Medium speed (m/s) Low speed (m/s) High speed (m/s) Medium speed (m/s) Low speed (m/s) 1 3.70 3.10 2.80 4.20 3.45 3.15 2 3.10 2.80 2.50 3.30 3.10 2.70 3 2.75 2.40 2.10 1.10 0.90 0.80 4 3.20 2.90 2.50 1.20 1.10 1.00 5 3.00 2.80 2.60 1.20 1.20 1.10 Average 3.15 2.80 2.50 2.20 1.95 1.75 For performance evaluation and analysis experiment is performed in for different cases as following Case A. Two stage air Cooler In this process both pump and auxiliary pump was switched on air is first cooled sensibly then evaporative cooling is done, side panel of is covered with insulating medium so that there is no mixing of hot air from side panel. http://www.iaeme.com/ijmet/index.asp 332 editor@iaeme.com

Performance Evaluation of Two Stage Air Cooler In Different Table 2 DBT and WBT at different points at different velocity for two stage air Cooler Average Velocity DBT WBT 1 3 1 2 3 1 3 High 3.15 2.20 31.5 27.5 21.9 22.6 20.50 Medium 2.80 1.95 31.5 27.4 22.2 22.9 20.7 Low 2.50 1.75 31.5 27.4 23.2 23.2 21.0 Case B. Conventional Cooler In this process auxiliary pump is switched off so only evaporative cooling of air is done. Side panel of is covered with insulating medium so that there is no mixing of hot air from side panel. Table 3 DBT and WBT at different points at different velocity for Conventional Cooler Average Velocity DBT WBT 1 3 1 3 1 3 High 3.15 2.20 31.5 24.0 22.5 21.4 Medium 2.80 2.00 31.5 24.3 22.8 21.7 Low 2.50 1.80 31.5 24.5 23.1 21.9 Table 4 Calculation of various parameters for Two stage Air Cooler Velocity (m/sec) Dry bulb temperature ( ) Wet bulb temperature ( ) Relative humidity (%) 1 3 1 2 3 1 3 1 3 High 3.15 2.2 31.5 27.5 21.9 22.6 20.5 46.40 87.37 Medium 2.8 1.95 31.5 27.4 22.2 22.9 20.7 47.92 87.46 Low 2.5 1.75 31.5 27.4 22.5 23.2 21.0 49.46 87.55 Dew point temperature Specific humidity (kg/kg ) Mass flow rate of air (kg/sec) Specific volume (m 3 /Kg) 1 3 1 3 1 3 1 3 High 18.62 19.70 0.01346 0.01443 0.3540 0.3563 0.8809 0.8844 Medium 19.13 20.20 0.01392 0.01472 0.3114 0.3154 0.8815 0.8556 Low 20.33 20.22 0.01437 0.01501 0.2805 0.2830 0.8821 0.8569 Specific enthalpy (KJ/Kg) H (kj/kg ) w (kg/kg ) Make up water (kg/hr) Area (m 2 ) 1 3 (1-3) (3-1) 1 3 High 66.10 58.67 7.43 9.67*10-4 1.2441 0.099 0.1384 Medium 67.26 59.71 7.55 8.00*10-4 0.9083 0.099 0.1384 Low 68.43 60.43 7.67 6.40*10-4 0.6462 0.099 0.1384 http://www.iaeme.com/ijmet/index.asp 333 editor@iaeme.com

Mohammad Ul Hassan Energy consumption Kwh Time to refill water tank (hr) Carnot COP COP High 0.201 24:54 30.71 13.20 Medium 0.196 34:07 31.72 12.00 Low 0.191 47:54 32.46 11.36 Table 5: Calculation of various parameters for Conventional Cooler Velocity (m/sec) Dry bulb temperature Wet bulb temperature Relative humidity (%) 1 3 1 2 3 1 3 1 3 High 3.15 2.2 31.5 31 24.0 22.5 21.4 45.89 79.56 Medium 2.8 2.0 31.5 31 24.3 22.8 21.7 47.41 79.70 Low 2.5 1.8 31.5 31 24.5 23.1 21.9 48.95 80.53 Dew point temperature Specific humidity (kg/kg ) Mass flow rate of air (kg/s) Specific volume (m 3 /kg) 1 3 1 3 1 3 1 3 High 18.44 20.25 0.01331 0.01493 0.3527 0.3535 0.8841 0.8612 Medium 18.96 20.57 0.01376 0.01524 0.3145 0.3193 0.8813 0.8624 Low 19.47 20.93 0.01422 0.01559 0.2806 0.2885 0.8819 0.8635 Specific enthalpy (kj/kg ) H (kj/kg ) w (kg/kg ) Make up water (kg/hr) Area (m 2 ) 1 3 (1-3) (3-1) 1 3 High 65.72 62.12 3.60 1.62*10-3 2.0616 0.099 0.1384 Medium 66.87 63.20 3.67 1.48*10-3 1.7012 0.099 0.1384 Low 68.04 64.30 3.74 1.37*10-3 1.42282 0.099 0.1384 Energy consumption Kwh Time to refill water tank (hr) Carnot COP COP High 0.183 15:02 39.6 6.9540 Medium 0.178 18:13 41.29 6.5833 Low 0.173 21:47 42.5 6.2369 RESULT AND DISCUSSION Variation of Temperature at Outlet of Cooler with Fan speed For data ref table no 4 and 5 http://www.iaeme.com/ijmet/index.asp 334 editor@iaeme.com

Minimum temperature attain Performance Evaluation of Two Stage Air Cooler In Different 25 24 23 22 21 20 Minimum temperature attain v/s speed 24 24.3 24.5 21.9 22.2 22.5 High Medium Low Effects Reason Temperature attained in Two Stage Air Cooler is lower than Conventional Cooler. As velocity/speed increases degree of cooling is increase In Two Stage Air Cooler the air is pre-cooled sensibly in the heat exchanger so the better cooling is performed this departure of temperature may be better explain by psychometric chart. Increased velocity provides increase of Reynolds no thence increase heat transfer coefficient and better cooling. In high velocity/speed some water droplets may not find sufficient time for evaporation and at the exit air is sensibly cooled This departure may be considered due to water spray at wet bulb temperature provides sensible cooling of air which has already humidified adiabatically. Mass Flow Rate at Different Data ref table no 4 and 5 http://www.iaeme.com/ijmet/index.asp 335 editor@iaeme.com

Change in enthalpy Mass flow rate Kg/sec 0.3563 0.3535 0.3154 0.3193 0.2831 0.2885 Mohammad Ul Hassan Mass flow rate at different spped 0.4 0.3 0.2 0.1 0 High Medium Low m/sec Two stage air Conventional Effect As the velocity decreases mass flow rate also decreases Reason: Mass flow rate decreases with decreased velocity because area of inlet and outlet is constant so mass flow rate varies according to velocity. Variation in change in enthalpy Data ref table no 4 and 5 Change in enthalpy v/s speed 10 5 0 7.43 7.55 7.67 3.6 3.67 3.74 High Medium Low Two stage air Conventional Effect Change in enthalpy for incoming and outgoing air in combined arrangement is more than direct cooling arrangement. Change in enthalpy increases with decrease in speed for the same setup. The change in enthalpy for Conventional Cooler should be zero because it is an adiabatic cooling process. Reason The incoming air condition is same for both the arrangement but the outgoing air in former case is much lower than Conventional Cooler so in case of Two Stage Air Cooler arrangement change in enthalpy is more. Refrigeration Effect Data ref Table no 4 and 5 http://www.iaeme.com/ijmet/index.asp 336 editor@iaeme.com

Energy consumption in Kwh 0.183 0.178 0.173 0.201 0.196 0.191 Refrigeration effect Performance Evaluation of Two Stage Air Cooler In Different 3 2 1 Refigeration effect v/s 2.6473 2.38127 2.27 1.2726 1.17183 1.07899 Two stage air Conventional 0 High Medium Low Effect Reason Refrigeration effect for Two Stage Air Cooler is more than Conventional Cooler. Refrigeration effect decreases with decreased speed. Since the change in enthalpy in case of Two Stage Air Cooler is more than Conventional Cooler only. So refrigeration effect in combined process is also more. As mass flow rate decreases with decrease in speed so the refrigeration effect also decreases with decrease in speed Energy Consumption Data ref Table no 4 and 5 Energy consumption v/s speed 0.21 0.2 0.19 0.18 0.17 0.16 0.15 Two stage air Convention al m/s Effect Reason Energy consumption for Two Stage Air Cooler is more than Conventional Cooler only. The energy consumption is decreases with decrease in velocity. Energy consumption for Two Stage Air Cooler is higher than direct cooling only because in former case along with fan and primary pump secondary pump is also running but in direct cooling secondary pump is not running so energy consumption is less. http://www.iaeme.com/ijmet/index.asp 337 editor@iaeme.com

Make up water required per hour COP Mohammad Ul Hassan Energy consumption by the fan is less for lower speed so it decreases with decreasing speed. Variation of COP with Data ref Table no 4 and 5 15 10 5 0 COP v/s 13.206 11.995 11.3644 6.954 6.583 6.237 High Medium Low (m/s) Two stage Air Cooler Conventional Cooler Effects 1. The COP for Two Stage Air Cooler is more than the Conventional Cooler only. 2. The COP for the same set up decreases with the decrease in speed. Reason Instead of energy consumption is more in case of Two Stage Air Cooler the COP is more because as compare to energy consumption the cooling is more in this case so the refrigeration effect is also more hence COP is more in case of Two Stage Air Cooler. COP decrease with the decrease in speed in both the cases because effect of the decrease in energy consumption with decrease in speed is less as compared to the effect of decrease of refrigeration effect Make up Water Requirement As in the cooling of air is by the process of evaporative cooling so the water evaporated continuously so make up water is need after particular interval of time according to arrangement and use of. Data ref Table no 4 and 5 Make water requirement v/s 2.5 2 1.5 1 0.5 0 2.0616 1.2441 1.7012 1.42282 0.9083 0.5502 High Medium Low Two stage Air Cooler Conventional Cooler http://www.iaeme.com/ijmet/index.asp 338 editor@iaeme.com

24:54:00 15:02 18:13 34:07:00 21:47 47:54:00 Performance Evaluation of Two Stage Air Cooler In Different Effect Make up water requirement is more for Conventional Cooler than Two Stage Air Cooler. The makeup water requirement for the same set up decreases with the decrease in speed for both the process. Reason Difference in specific enthalpy at inlet and outlet of is more in case of Conventional Cooler only because at outlet specific enthalpy is more in case of Conventional Cooler. For the same setup as the speed decreases the difference in specific enthalpy decreases along with this the mass flow rate of air also decreases so the makeup water require is also less. Makeup Water Recharge Time (May vary according to prevailing ambient condition) As the makeup water needed so the tank has to be refill after particular interval of time depending on the capacity of tank and use of. In this the tank capacity is 31 litres so time to refill the tank for different arrangement and different speed has been given below in tabular form. Data ref Table no 5 and 6 tme for reffiling of tank require v/s Low Medium High 0:00:00 24:00:00 48:00:00 Time after which refilling require Conventinal Cooler Comparison of COP of Simple Air Cooler v/s Two Stage Air Cooler v/s Conventional Window Air Conditioner APPLIANCES COP Two Stage Air 13.206 Simple Air Cooler 6.954 Window AC 2.846 http://www.iaeme.com/ijmet/index.asp 339 editor@iaeme.com

COP Mohammad Ul Hassan COP for different appliances 15 10 5 13.206 6.954 2.846 0 Two StageAir Conventional Air Cooler Window AC Appliances CONCLUSION Following are the fruitful result outcome of indirect two stage air their details have been provided in result and discussion. Effective temperature decreases COP increases up to 13 which are significantly higher than normal and conventional air conditioner. Refrigeration effect increases. Makeup water recharges time increases for the same configuration has been obtained. In two stage air with cover noise has been drastically reduce by the increase damping effect of covers Specific humidity increase is significantly lower than that of in case of Conventional Cooler. RECOMMENDATIONS Two stage indirect air is energy effective, eco friendly, cost effective cooling system and with some further modification it may be hope as replacement of air conditioner. In direct expected limit lower temperature was 22.6 where as experimentally the temperature attains is 24. In indirect system the expected temp was 20.5 where as the actual temperature attain is 21.9 less than the wet bulb temperature with lesser relative humidity than 100%. REFERENCES [1] Dowdy j. A. and Karbash N. S. (1987). Experimental determination of heat and mass transfer coefficients in rigid imperegnated cellulose evaporative media, ASHRAE Transactions, 93, Part 2, pp 382 395. [2] Chen P. L., Qin H. M., Huang Y. J., Wu H. F. (1991). Ä heat and mass transfer model for thermal and hydraulic calculations of indirect evaporative performance, ASHRATE Transactions, 97, Part 2, pp 852 865. [3] Peterson J. L. (1993), An effectiveness model for indirect evaporative s, ASHRAE Transactions, 99, Part 1, pp 392 399. [4] El-Dessouky H. T. A., Al-Haddad A., Juwayhel F.I.(1996). Thermal and hydraulic performance of a modified two-stage evaporative, Renewable Energy, 7(2), pp 165 176. [5] Maheshwari G. P., Al-Ragom F., Suri R. K. (2001), Energy saving potential of an indirect evaporative, Applied Energy, 69(1), pp 69 76. http://www.iaeme.com/ijmet/index.asp 340 editor@iaeme.com

Performance Evaluation of Two Stage Air Cooler In Different [6] El- Dessouky H., Al Zeefari A. (2004), Performance analysis of two stage evaporative s, Chemical Engineering Journal 102(3), pp 255 266. [7] Camrago J. R., Ebinuma C. D., Silveria J. L. (2005), Experimental performance of a direct evaporative operating during summer in Barzilian City, International Journal of Refrigeration, 28 (7), pp 1124 1131. [8] Jain D., (2007), Development and testing of two stage evaporative, Building and Environment, 42(7), pp 25 54. [9] Heidarinejad G., Bozorgmehr M., Delfani S., Esmaeelian J. (2009). Experimental investigation of two stage indirect/ Convetional Cooler system in various climatic conditions. Building and Environment, 44(10), pp 2073 2079. [10] Principle of Evaporative Cooling System, 2012,PDH online Course M231 (4 PDH) [11] Mohd. Rehan Khan and Dr. Ajeet Kumar Rai, An Experimental Study of Exergy In A Corrugated Plate Heat Exchanger. International Journal of Mechanical Engineering and Technology, 6(11), 2015, pp. 16 22. [12] Akshay Khot, Analysis of Various Designing Parameters for Earth Air Tunnel Heat Exchanger System. International Journal of Mechanical Engineering and Technology, 5(12), 2014, pp. 118 125. [13] ASHRAE Handbook, 1995, chapter47, Evaporating Air Cooling notes. http://www.iaeme.com/ijmet/index.asp 341 editor@iaeme.com