evaporative cooling system

1. Evaporative cooling
system
SUBMITTED BY
ROHIT
SATYADEV YADAV
RUPREET KAUR

2. INTRODUCTION
AN EVAPORATIVE COLLER IS A DEVICE THAT COOLS AIR THROUGH
THE EVAPORATION OF WATER .
EVAPORATIVE COOLING DIFFERS FROM TYPICAL AIR CONDITIONING
SYSTEM, WHICH USE VAPOR-COMPRESSION OR ABSORPTION
REFRIGENRATION CYCLE.

4. PRINCIPLES
EVAPORTIVE COOLERS LOWER THE TEMPERATURE OF AIR
USING THE PRINCIPLE OF EVAPORATIVE COOLING, UNLIKE
TYPICAL AIR CONDITIONING SYSTEMS WHICH VAPOR-
COMPRESSION REFRIGERATION OR ABSORPTION
REFRIGERATION.
EVAPORATIVE COOLING IS THE CONVERSION OF LIQUID
WATER INTO VAPOR USING THE THERMAL ENERGY IN THE
AIR, RESULTING IN A LOWER AIR TEMPERATURE.

5. WORKING
• A MECHANICAL DIRECT EVAPORATIVE
COOLER UNIT USES A FAN TO DRAW AIR
THROUGH A WETTED MEMBRANE, OR PAD,
WHICH PROVIDES A LARGE SURFACE AREA
FOR THE EVAPORATION OF WATER INTO
THE AIR.
• WATER IS SPRAYED AT THE TOP OF THE
PAD SO IT CAN DRIP DOWN INTO THE
MEMBRANE AND CONTINOUSLY KEEP THE
MEMBRANE SATURATED.
• ANY EXCESS WATER THAT DRIPS OUT
FROM THE BOTTOM OF THE MEMBRANE IS
COLLECTED IN A PAN AND RECIRCULATED
TO THE TOP.
• SINGLE STAGE DIRECT EVAPORATIVE
COOLERS ARE TYPICALLY SMALL IN SIZE AS
IT ONLY CONSISTS OF THE MEMBRANE,
WATER PUMP, AND CENTRIFUGAL FAN.

6. TYPES OF EVAPORATIVE COOLING
1. DIRECT EVAPORATIVE COOLING
2. INDIRECT EVAPORATIVE COOLING
DIRECT EVAPORATIVE
COOLING: IS USED TO LOWER THE
TEMPERATURE AND INCREASE THE HUMIDITY OF AIR BY
USING LATENT HEAT OF EVAPORATIVE, CHANGING LIQUID
WATER TO WATER VAPOR. IN THIS PROCESS, THE ENERGY
IN THE AIR DOES NOT CHANGE. WARM DRY IS CHANGED
TO COOL MOIST AIR.
THE HEAT OF THE OUTSIDE AIR IS USED TO EVAPORATE
WATER. THE RH INCREASES TO 70% TO 90% WHICH
REDUCES THE COOLING EFECT OF HUMAN PERSPIRATION.
THE MOIST AIR HAS TO BE CONTINUALLY RELEASED TO
OUTSIDE OR ELSE THE AIR BECOMES SATURATED AND
EVAPORATION STOPS

7. INDIRECT COOLING
INDIRECT EVAPORATIVE COOLING PROCESS, TWO
STREAMS OF AIR- PRIMARY AND SECONDARY ARE USED.
THE PRIMARY AIR STREAM BECOMES COOLED AND
HUMIDIFIED BY COMING IN DIRECT CONTACT WITH THE
WETTED SURFACE, WHILE THE SECONDARY STREAM
WHICH IS USED AS SUPPLY AIR TO THE CONDITIONED
SPACE, DECREASES ITS TEMPERATURE BY EXCHANGING
ONLY SENSIBLE HEAT WITH THE COOLED AND HUMIDIFIED
AIR STREAM.
THE MOISTURE CONTENT OF THE SUPPLY AIR REMAINS
COSTANT IN AN INDIRECT EVAPORATION COOLING
SYSTEM, WHILE ITS TEMPERATURE DROP

10. ADVANTAGE
• LESS EXPENSIVE TO INSTALL AND OPERATE.
• SUBSTANTIALLY LOWER OPERATING AND POWER COSTS. ENERGY SAVING CAN BE AS
HIGH AS 75%.
• EASE OF FABRICATION AND INSTALLATION.
• LOWER MAINTENANCE COSTS
• BETTER AIR DISTRIBUTION IN THE CONDITIONED SPACE DUE TO HIGHER FLOW RATES.
• VERY ENVIRONMENT FRIENDLY AS SO HARMFUL CHEMICALS ARE NOT USED.

11. DISADVANTAGE
 MOST EVAPORATIVE COOLERS ARE UNABLE TO LOWER THE AIR TEMPERATURE AS
MUCH AS REFRIGERATED AIR CONDITIONING.
 HIGH DEWPOINT CONDITIONS DECREASE THE COOLING CAPABILITY OF THE
EVAPORATIVE COOLER.
 EVAPORATIVE COLLERS REQUIRE A CONSTANT SUPPLY OF WATER TO WET THE PADS.
 SINCE THE REQUIRED AIR FLOWS RATES AS MUCH LARGER, THIS MAY CREATE DRAFT
AND OR HIGH NOISE LEVEL IN THE CONDITIONED SPACE.
 PRECISE CONTROL OF TEMPERATURE AND HUMIDITY IN THE CONDITIONED SPACE IS
NOT POSIBLE.
 MAY LED TO HEALTH PROBLEM DUE TO MICRO-ORGANISMS IF THE WATER USED IS
NOT CLEAN OR WETTED SURFACE ARE NOT MAINTAINED PROPERLY.