DESIGN AND PERFORMANCE EVALUATION OF AN EVAPORATIVE HEAT EXCHANGER
A.O. MURITALA, S.O. OBAYOPO, S.K. FASHOGBON, O.T. POPOOLA*, S.A ADIO
Department of Mechanical Engineering, Obafemi Awolowo University,Ile-Ife, Nigeria.
International Conference on Innovations in Engineering and Technology (IET 2011)UNIVERSITY OF LAGOS, FACAULTY OF ENGINEERING, AKOKA, LAGOS, Nigeria
INTRODUCTION
Evaporative Cooling
• The increased air filtration qualities • Simplified operation and maintenance• Lower costs• Lower energy usage • Less greenhouse gas• No CFC's or HFC's
Evaporative Cooler
• Cabinet• Reservoir Tank• Pad• Blower• Electric Motor • Pump
Fig 1: Schematic diagram of an evaporative cooler
Objective
• To design and construct an evaporative cooler.• To evaluate the performance of the cooler.
DESIGN
General
•Reduction in the discomfort index by 90% •Required fan power is linearly dependent on the floor area to be cooled.•Building heat balance (EC sizing)
SOLAR HEAT + HEAT FROM EQUIPMENT & PEOPLE = HEAT REMOVED BY EAC
Cabinet Reservoir Tank• Galvanized iron sheet• 50x55x70 cm3
• One sided Cabinet
Reservoir Tank• Inlet• Outlet• (50 x 55 x 23) cm3
Evaporative Pads• Aluminum fins• 35 x 47 x 10 cm3
Blower
Electric Motor • half-horse power connected by a direct drive• 2 speed motor• 220 V
Pump
• re-circulating surface pump • 0.5 horse power• Water pump screen
Plate 1: The evaporative cooler housing cabinet
Plate 2: The designed evaporative cooler
EVALUATION
Monitored Parameter
• Room size 305 x 254 x 203 cm³ • Outside air temperature• Evaporative cooler inlet air temperature and
humidity• Evaporative cooler outlet air temperatures and
humidity• Water temperature in the evaporative cooler
reservoir• Evaporative pad surface temperature • Air speeds & mass flow rate
RESULTS
Table 1: Dry and Wet Bulb Temperature, Humidity Ratio humidity gain and Saturation Effectiveness
Saturation Effectiveness & External Dry-Bulb Temperature
• increase in saturation effectiveness as the external db temp increases
• evaporative cooler is more efficient at higher outside air db temp
Saturation Effectiveness & Humidity Gain
• The saturation effectiveness increased as the humidity gain increases
Humidity Gain & External Dry Bulb Temperature
• increased gain in humidity ratio at higher external db temp
0.003
0.0035
0.004
0.0045
0.005
0.0055
32 33 34 35 36 37 38 39 40
Hum
idity
gai
n (k
g/kg
)
External dry bulb temperature (oC)
Fig 4.3: Humidity gain as a function of external dry bulb temperature
CONCLUSION• The saturation effectiveness of pad determined from the experimental result
falls between the ranges of 70-83.3%.
• the pad employed for the construction of the cooler is efficient and reliable.
• The designed evaporative coolers can maintain cooled spaces at temperatures below ambient air temperatures.
• The performances of the evaporative cooler were significantly affected by weather conditions.
• The overall cooled room temperature depression from ambient air temperature reached up to 11 0C, and ambient air temperatures varied between 22–33 0C.
Thank You !!!!
