Indirect evaporative cooling works on the same principle as direct evaporative cooling lowering air temperature by water Evaporation. The major difference in an indirect system is that it uses an heat exchanger to cool the air supplied to the working space. The evaporative cooling cycle occurs in the humidification section.
How a an indirect evaporative cooling system works is explained sequentially:
- In one type of System ,Hot outside air is blown over a heat exchanger through which cold water is supplied . This type of heat exchanger features a series of metal tubes through which cold water is supplied and hot air blown over the tubes and fins. As hot air passes over these tubes, its sensible heat is removed. After passing over the tubes, the cool ,dry is delivered to living space.It not only lowers down dry bulb temperature but wet bulb temperature as well.Indirect Evaporative cooler find application where low humid but 100% fresh air is needed for cooling.
- The another important point is that the hot air is cooled without gaining any extra humidity.
Indirect evaporative cooling provides cool air to interior spaces with less Relative humidity compared to direct evaporative cooling. This, cooling method is more suitable for areas where additional humidity is not desirable . Since indirect evaporative cooling requires two pumps rather than one, it consumes little more electricity than direct evaporative cooling.
In second type of Indirect Evaporative Cooling system -primary warm air flows in enclosed channels .It gives up its heat to water films flowing down the other side of the polymeric plates. A secondary air stream flowing in the direction opposite to the water evaporates water before it is exhausted outside. Thus, in Indirect Evaporative cooler the primary air is cooled without any moisture addition .
Advantages of Indirect Evaporative cooling
- Indirect Evaporative coolers delivers 5 Deg.C more Cooling and adds 60% less moisture than DEC.
- Indirect Evaporative Cooling requires 30-40% less air .
- A Make in India Product
- Indirect Evaporative Cooler require 40-60 percent lower energy consumption as compared to conventional air conditioning systems
- 100 percent fresh, clean, cool air
- Indirect Evaporative cooling Creates more comfortable conditions for employees and processes
- Main advantage of indirect Evaporative cooling is that it do not use any harmful gaseous .
- Lower supply air temperatures with much lower addition of moisture to the supply air as compared to air washers
- Increased productivity of employees
- Excellent Indoor Air Quality (IAQ) and no Sick Building Syndrome (SBS)
Specification of IDECool 4
|Model- Type||IDECool 4|
|Construction||Single skin 4mm thick Aluminum Composite Panels(ACP) appliance
white, framed in a 30x 30 mm extruded aluminum structure and GI base
|Air flow Machine Outlet- in CFM/CMH||4000 / 6800|
|Area cooled (sq feet)||800 – 1000|
|Available external static pressure in mm of Wg||5|
|Type of Blower||Backward Curve belt driven fan|
|Blower motor connected load kW||1.5 kW|
|Blower motor consumption load kW||1.37 kW|
|10 Filtration||HDPE mesh of 60microns will be used behind the Louvers|
|Pump||2 nos. submersible, 50watts single phase pump.|
|Dimensions W x L x H (mm)||1100x1900x(1450+150)|
|Unit operating Weight in Kg||350|
|Power supply||Three Phase 415V,50Hz.with connected load of 1.6kW.|
|Controller||Microcontroller with corded remote controller (20 m wire length)|
|RH control available||Yes manual RH control available|
|Additional features available on request.|
|Single phase power supply||Available on request|
|Variable frequency drive.|
|Auto drain system.|
|Differential pressure for air filters|
|Auto bleed-off facility|
|UV unit for tank water|
|Capacity||4000 CFM||2 TON|
|Power||1.5 kW||2.0 Kw|
|Covered Area||800 sqft||800 sqft|
|Air Changes Per Hour||30||30|
|No. of Machine Required||1||4|
|Electricity Unit Consumption per year (10 hrs, 300 days)||4500 kw||24,000 kw|
|Total Electricity Cost (in Rs.)(Assuming Rate @ Rs 8/Unit)||Rs. 36,000 /-||Rs. 1,92,000 /-|
|Saving on Electricity Cost per year ( in Rs.)||Rs. 1,56,000/-||Nil|
|Running Cost Saving (%)||81%||NIL|
|PAYBACK PERIOD||11 Months|
Direct evaporative cooling (Single Stage Cooling)
Indirect evaporative cooling
What is direct Evaporative Cooling?
With direct evaporative cooling, outside air is blown through a Honeycomb cooling pad and cooled by evaporation process. This cooled air is circulated by a blower ,further.
Direct evaporative cooler reduces the dry bulb temperature* but the wet bulb temperature** stays the same. However,it adds moisture to the air .
*dry bulb: Sensible air temperature (as measured by a Thermometer).
**wet bulb: The lowest air temperature achievable by evaporative Air Cooilng System.
What is Indirect Evaporative Cooling ?
In Indirect evaporative cooling Hot Air and water travel in different channels .They do not come directly in contact with each other, hence the name Indirect Evaporative Cooling.
In Indirect Evaporative Cooling stage, warm primary air cools by losing its heat to a thin water film on the other side of a conducting surface. And another air stream called Secondary or Scavenging air moves upward through the falling water and evaporates this water.It converts most of the sensible heat into latent heat before it is exhausted to the outside. Thus ,the primary air is cooled without coming in contact with the water stream. Hence, IEC reduces the dry bulb temperature, wet-bulb temperature, and the enthalpy of the primary air without adding any moisture to it. Moreover ,Indirect Evaporative cooling are more effective and energy efficient.
Indirect-direct evaporative cooling ( Two Stage Cooling )
In Indirect Evaporative cooling, the primary air is cooled without coming in contact with water. Hence in first stage air is cooled without adding any moisture to it. It is cooled further in the second stage with the direct evaporative cooling process .It ,however, in extra drop of 5 Degree c in temperature
What Temperature reduction is achievable using indirect Evaporative Cooling and direct evaporative cooling ?
First, calculate the dry bulb and wet bulb temperatures achievable with indirect evaporative cooling:
1. Temp drop achievable = (dry bulb – wet bulb ) x (efficiency of indirect module)
Example: (42 degrees C- 23.5degrees C) x .7 = 13 degreesC.
2. Achievable temp = dry bulb – temp drop achievable
Example: 42 degrees – 13 degrees = 29 degrees DB/19.5 degrees WB.
3. Starting DB: 42 degrees
Ending DB: 29 degrees
Then use the dry bulb/wet bulb values from step 3 to calculate the dry bulb/wet bulb temperatures achievable with direct evaporative cooling:
4. Temp drop achievable: (dry bulb – wet bulb ) x (efficiency of the media)
Example: (29 degrees – 19.5 degrees) x .9 = 8.6 degreesC.
5. Achievable temp = dry bulb – temp drop achievable
Example: 29 degrees – 8.6 degrees = 20.4 degrees DB/19.5 degrees WB.
6. Total temperature reduction using indirect/direct evaporative cooling:
Starting DB: 42 degrees C
Ending DB: 20.4 degrees C