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 !!!!