Evaporatif Klima Hakkında Bilgiler

www.erdincklima.com The Concept Evaporative cooling is a process in which hot dry air is cooled by evaporating water into it. Air naturally soaks up water. This water requires a great deal of energy to change from a liquid to a gas. This energy has to come from the air during this evaporation. The effect of this is that on a typical hot day in the UK, air at 30°C and 35%RH will be cooled down to 20 °C. This natural process is exploited by all mammals – sweat evaporates from the surface of the skin and the skin is cooled. For thousands of years it has been used to cool buildings and tents by hanging a wet cloth over an open door or window. As the air passes through the weave of the cloth the air is cooled and the atmosphere is made more comfortable.
	A modern evaporative cooler consists of a fan which draws hot air across wet filter pads and discharges the cool air to its point of use. As warm air passes over wet filter pads water naturally evaporates into the air. The air is cooled as it gives up the heat required to evaporate the water.
A more detailed explanation of the above is given in Section 9 Why does an evaporative cooler work in a UK Climate? The pattern of the relationship between temperature and relative humidity on a typical hot day in Northern Europe is shown below.
It can be seen that the highest temperature coincides with the lowest humidity. This gives the greatest cooling when it is needed the most. This also has a smoothing effect on the temperature of the air coming off the cooler which leads to more stable conditions. Comparison with Conventional Air Conditioning Evaporative Air Cooling Refrigerated Air Conditioning Uses only 10% of the electricity compared with conventional air conditioning Uses large amounts of electrical power because of compressor. As temperature rises efficiency improves As temperature rises efficiency reduces Cooling capacity is only limited by the air conditions. Up to 50KW of cooling can be achieved with only 1 KW of electricity used Cooling is limited by theoretical Coefficient of Performance which means a maximum of 3.5 KW of cooling for 1 KW of electricity consumed Open doors and windows do not affect performance Open doors and windows significantly reduce performance. Uses no harmful gases for its function. Uses environmentally harmful gases. Avoiding relative humidity below 50% significantly reduces static electricity problems Leads to low relative humidity which can create high static electricity conditions Few moving parts – one fan, one pump and three solenoid valves Many moving parts including complex and expensive components such as the compressor Easy and simple to service. More difficult and expensive to service. Always supplies 100% fresh air. Only supplies about 15% fresh air. 85% is re-circulated. It is not fresh. Air only cooled once. Air cooled many times. Has no upper limit on temperature High ambient temperatures can lead equipment to shut down due to compressor overload Lower purchase cost. Higher cost to purchase. Have bigger fans - pump large amounts of air. Smaller fans - pump less air. Temperature reduction limited by ambient Relative Humidity. At higher Relative Humidities cooling is reduced due to greater latent heat load compared to sensible load. Provides flow of fresh cool air. Provides cool, recirculated, stale air. Provides stable relative humidity levels which are more comfortable to work in Can lead to low Relative Humidity which is not comfortable. Simple to create positive pressure in buildings giving hygiene and control benefits More difficult to create positive pressure with recirculation systems Evaporative Cooling Performance Air and Water Air acts like a sponge to water. Just as spoe is limited in the amount of water it can absorb air is also limited. A key difference is the hotter the air the more water it can support before it becomes ‘saturated’ and can hold no more water. It can be seen from the data below that this amount of water dramatically increases as the temperature increases. The maximum amount of water supported by air at atmospheric pressure is: 0°C 10°C 20°C 30°C 40°C 5g per cubic metre 10g/m3 20g/m3 34g/m3 62g/m3 The term relative humidity refers to the actual amount of water in the air compared with its maximum or saturated value, and is stated as a percentage. e.g. Water at 30°C with 17g of water in it is 50% RH Many engineers use a Psychrometric chart to understand the relationship between air and water. This chart is explained in detail section 17 Theoretical Performance The performance of an evaporative cooler is dependent upon both the temperature and the relative humidity of the air passing over the pads together with the efficiency of the pads. The theoretical cooling is shown below. The higher the temperature and lower the relative humidity the greater the cooling effect Actual Performance The graph below shows an actual example of performance of a cooler. Legionnaires’ Disease Background It is estimated that there are 20 million evaporative cooling systems in the Western world. There has never been a documented case of Legionnaires’ disease associated with a wetted media evaporative cooler. Legislation in the United Kingdom is more stringent than anywhere else in the World. EcoCooling has developed the equipment and systems to comply with this legislation in a practical and relevant format. Specific Legislation Relating to Legionnaires’ Disease In addition to the Health and Safety at Work Act (HSWA), the Control of Substances Hazardous to Health Regulations (COSHH) and the Management of Health and Safety at Work Regulations (MHSWR) the HSC produce an Approved Code of Practice (ACOP) Legionnaires’ Disease: The control of legionella bacteria in water systems L8. It is the legal duty of employers and the responsibility of the managers of premises to comply with the above. Compliance with Legislation: The steps required in fulfilling statutory duties are: Completion of a Risk Assessment The preparation of a scheme for preventing or controlling the risk Implementation, managing and monitoring of precautions Maintenance of records Appointment of a responsible manager About Legionnaires’ Disease What is legionnaires' disease? Legionnaires' disease is a type of pneumonia. It was named after an outbreak of severe pneumonia which affected a meeting of the American Legion in 1976. It is an uncommon but serious disease. The illness occurs more frequently in men than women. It usually affects middle-aged or elderly people and it more commonly affects smokers or people with other chest problems. Legionnaires' disease is uncommon in younger people and is very uncommon under the age of 20. About half the cases of legionnaires' disease are caught abroad. The other half are the result of infections acquired in the UK . How do people get it? The germ which causes legionnaires' disease is a bacterium called Legionella pneumophila. People catch legionnaires' disease by inhaling small droplets of water suspended in the air which contain the Legionella bacterium. However, most people who are exposed to Legionella do not become ill. Legionnaires' disease does not spread from person to person. Where does it come from? The bacterium which causes legionnaires' disease is widespread in nature. It mainly lives in water, for example ponds, where it does not usually cause problems. Outbreaks occur from purpose-built water systems where temperatures are warm enough to encourage growth of the bacteria, eg in cooling towers, evaporative condensers and whirlpool spas (tradename Jaccuzi) and from water used for domestic purposes in buildings such as hotels. Most community outbreaks in the UK have been linked to installations such as cooling towers or evaporative condensers which can spread droplets of water over a wide area. These are found as part of air-conditioning and industrial cooling systems. What measures are there to control legionnaires' disease? To prevent the occurrence of legionnaires' disease, companies which operate these systems must comply with regulations requiring them to manage, maintain and treat them properly. Amongst other things, this means that the water must be treated and the system cleaned regularly. What are the symptoms? The symptoms of legionnaires' disease are similar to flu high temperature, feverishness and chills; cough; muscle pains; headache; and leading on to pneumonia, very occasionally diarrhoea and signs of mental confusion How is it treated? The illness is treated with an antibiotic called erythromycin or a similar antibiotic. The EcoCooling Approach to Managing Legionnaires’ Disease Evaporative Cooling System Design: The design of all EcoCooling equipment takes the ACOP guidance into account. This includes the following which would not normally be included on a standard installation of an evaporative cooling system: A water treatment system A process control system minimising build up of potential contamination Materials of construction which are corrosion resistant System Management: Work Space Cooling provides all clients with the following: A fully documented risk assessment package A prevention and control system for water management and equipment care based on the following principles Hygiene and Evaporative Coolers EcoCooling believes that hygiene is the most important factor in providing a safe and secure system which provides compliance with legislation and peace of mind. Hygiene The maintenance of a clean and safe evaporative cooler is achieved by the following: Avoidance of stagnant water Low water operating temperature Avoidance of corrosion and scaling No production of aerosols Maintenance Use of a biocide or UV Each of the above points will be detailed below Avoidance of stagnant water: Since no dead legs exist in the system no stagnation occurs during normal operation of an EcoCooling evaporative cooler. When a unit is switched off the system automatically drains. A low level probe constantly monitors the water level when shut down. When a system is first powered up the first operation is to empty the sump. Low water operating temperature: The temperature of the water circulating in the evaporative cooler is approximately the “wet bulb temperature” of the air passing over the filters. In practice this means that, in a temperate climate, the water temperature rarely goes above 20 0C as shown even when the air on temperature exceeds 35 0C It is generally accepted that Legionella is not a risk with water temperatures less than 20 0C Avoidance of corrosion and scaling: To prevent corrosion all water contact surfaces are either plastic or non-ferrous. EcoCooling evaporative coolers measure the water usage. When the water reaches a set point , determined on commissioning according to the local water quality, the sump empties automatically and replenishes with fresh water. This has the effect of preventing scale and removing of contaminants filtered from the air. During this drain cycle the sump empties completely to assist in the removal of any sediment which may be present in the sump. Use of Biocide: Growth of organisms filtered from the air is suppressed by supplying the evaporative cooler with water with a low level of biocide. No production of aerosols: The design of the EcoCooling coolers is such that only pure water evaporation occurs as the air passes over the filters. This removes the mechanism for the transmission of infections such as Legionnaires’ disease The maximum air velocity in an EcoCooling cooler is 1.9m/s. From the chart above it can be seen that the Munters maximum speed for avoidance of droplets is 3m/s. Thus a safety factor of over 50% is achieved. Maintenance: By the implementation of a programmed maintenance system the standards of hygiene are continued to provide a safe and secure system. Detailed maintenance procedures are provided to all users. Generic Risk Assessment The end user is ultimately responsible for performing their own risk assessments. This generic document is intended to provide technical details to support these assessments. Background The purpose of this document is to provide an understanding of the legionella control in EcoCooling evaporative coolers. Government guidelines which provide the basis for both design and risk assessment are explained. The prevention plan demonstrates the EcoCooling approach Government Guidelines With reference to the HSE publication ACoP L8: Legionnaires’ disease: The control of legionella bacteria in water systems, the following is the section which describes general methods of legionella prevention In general, proliferation of legionella bacteria may be prevented by: (a) avoiding water temperatures between 20 0C and 45 0C – water temperature is a particularly important factor in controlling the risks: (b) avoiding water stagnation, which may encourage the growth of biofilm; (c) avoid the use of materials in the system that can harbour or provide nutrients for bacteria and other organisms; (d) keeping the system clean to avoid the build-up of sediments which may harbour bacteria (and also provide a nutrient source for them); (e) the use of a suitable water treatment programme where it is appropriate and safe to do so; and (f) ensuring the system operates safely and correctly and is well maintained This document shall detail the approach taken to the above by EcoCooling in the design, commissioning, operation and maintenance of EcoCooling evaporative coolers. Note: This document is not intended to replace a risk assessment produced as a requirement of HSE ACoP L8 – Legionnaires’ disease: The control of legionella bacteria in water systems Prevention of Legionella in Evaporative Coolers Note that the following only applies to EcoCooling evaporative coolers. (a) Water Temperature Monitoring of the water the circulating water temperature shows that with air on temperatures to the cooler up to 40 0C the temperature of the water in the sump does not normally exceed 20 0C in the UK climate. Data demonstrating this is shown in the chart below: The above can be explained by the circulating water approaching the ‘wet bulb temperature’ of the air. In temperate climates the ‘wet bulb temperature’ rarely exceeds 20 0C and, in these rare instances, remains above this temperature for only a few hours. Note that when the cooler is switched off the sump automatically drains. This prevents the water rising to ambient temperature which may be in the 20 0C to 45 0C range. (b) Stagnation During normal cooling operation the water continuously circulates. The design of the cooler avoids any dead legs and so stagnation does not occur. When the unit is not operating the sump automatically drains. The unit is fully self draining and therefore no stagnation is possible. (c) Materials of Construction With the exception of the filter pads all water contact surfaces are manufactured from plastic or non ferrous materials. The Munters CelDek filter pads are manufactured from a cellulose material which is treated with ‘anti-rot' salts to resist biological deterioration and to give high absorbency. It is a rigid, self-supporting product. The pads are examined during programmed maintenance and replaced as necessary. (d) System Cleanliness As water evaporates both the levels of dissolved salts and solids increase. The volume of evaporation is measured using four level probes and, when a set concentration is reached, the sump is completely drained removing both the water which is approaching the scaling point and any other sediment or particles in the system. The sump is then refilled using fresh, clean water. Programmed maintenance includes cleaning of all water contact surfaces. (e) Water treatment programme Bromination can be added to provide additional microbiological security Whilst Legionella is not considered to be a risk below 20 0C other organisms can grow in these conditions. The purpose of a biocide or UV is to prevent the formation of bio-films which could play a role in the support of legionella bacteria. A brominator can be added which provides a residual minimum bromine level of 0.5 ppm in the sump. The process control system, using a system of level probes to calculate the concentration of water is set to prevent scale formation. (f) System Operation and Maintenance Operating instructions are provided with each installation. These include: Operating Instructions Brominator operating instructions Bromine level testing instructions EcoCooling can provide all chemicals and testing equipment required for the above. A detailed maintenance procedure is used for the cleaning, sanitisation and validation of the operation of the coolers. Summary The overall level of risk is dictated by the quality of the air being cooled. It is the air that can provide the seeding of legionella and nutrients for growth. With clean air the units are very low risk when all of the prevention and control activities described are adhered to. Generic Prevention and Control Plan Precaution Measure Action Avoid spray Design velocity of air over filter pads must not be exceeded No unauthorised or unspecified components to be used Water in unit must not enter fan Water level to be set to specification Unit to be installed horizontally Keep temperature of water below 20 0C Use fresh potable water Check on installation Drain when not in use Unit to be configured to drain when not in use. Avoid stagnant water Drain when not in use Unit to be configured to drain when not in use System must fully drain Unit must be installed horizontally Water presence must be monitored Use safe materials of construction All water contact materials shall be plastic or non ferrous (except pads) Use only specified components Keep water and system clean Do not allow salts to build up Use control system to monitor water concentration and drain automatically Do not allow solids to build up Solids removed as part of salinity control System should be cleaned of sediment as part of maintenance plan Minimise contamination from new installation Sanitise unit prior to use Prevent bio-films developing Use water treatment Prevent bacteria growth Use water treatment Use water treatment Biocide treat all incoming water Install brominator to treat all incoming water Maintain biocide concentration in system Make regular checks on bromine level Operate water system correctly and safely Adhere to instructions Provide end user with full documentation Installation Commissioning Operation Maintenance www.erdincklima.com

Evaporatif Klima Nasıl Hesaplanır?

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Evaporatif Klima Hesaplaması

Evaporative cooling is a completely natural way of producing refreshing cool air.

The EcoCooling range of evaporative coolers are:

• Simple

• Safe

• Low Cost

An ideal way of keeping people, buildings and processes cool.

Basics of Sizing Applications

There are a number of methods determining the number of evaporative coolers required:

• A ventilation system based on the number of air changes per hour
• Performing a heat balance on the building to calculate exhaust temperature
• Spot cooling

In order do complete any calculations both the temperature and the flow rate out of the cooler must be calculated. The method of determining the cooler outlet temperature is described in detail in Section 17. The flow rate of the coolers is dependent on the fan curve and the air distribution system. The principle of the calculation is shown below.

The fan curve for an axial fan, as fitted to all EcoCooling coolers, has the characteristic curve as shown by the blue line. Air distribution systems have a characteristic curve as shown by the green line. By using the design information from the air distribution system and the fan curve given in the cooler specification the actual flow rate can be established. In this case an air flow rate of just over 14,000m 3/hr (3.8m 3/s) is achieved at a static pressure of 150Pa

Specialist advice must be taken to establish the actual performance of the system.

Air Changes per Hour Method

This method calculates the number of coolers required based on the number of air changes per hour with a given working volume.

The number of air changes per hour required is based partially on experience and partially on the typical values shown on the table in the next part of this document.

The working volume is that underneath the discharge of the plenum chambers as shown by the blue shaded area in the diagram below.

Example calculation:

A bakery is 20m x 24m and it is proposed to fit ECP plastic external units with a minimum plenum discharge height of 3.5m.

Volume of working area of the building: 20 x 24 x 3.5 = 1680m 3

Target air changes per hour: 30

Target air flow per hour: 30 x 1680 = 50,400m 3/hr

Air flow rate of ECP16000 14,000 m 3/hr@150Pa

Nominal number of coolers required 50,400 / 14,000 = 3.6 = 4 coolers

Therefore the proposal would be 4 ECP16000 coolers together with balanced extract to maintain a small positive pressure.
Ventilation Rates with Air Velocities

Location Air Changes Per Hour

Assembly Halls 4 – 8
Bakeries 20 – 30
Banks 4 - 8
Bathrooms 6 - 10
Bedrooms 2 - 4
Billiard Rooms * 6 - 8
Boiler Rooms 15 - 30
Cafes and Coffee Bars 10 - 12
Canteens 8 - 12
Cellars 3 - 10
Changing Rooms - Main area 6 - 10
Changing Rooms - Shower area 15 - 20
Churches 1 - 3
Cinemas and Theatres * 10 - 15
Club rooms 10 - 12
Compressor rooms 10 - 20
Conference rooms 8 - 12
Dance halls 8 - 12
Dental surgeries 12 - 15
Dye works 20 - 30
Electroplating shops 10 - 12
Engine rooms 15 – 30
Entrance Halls & Corridors 3 - 5
Factories and Workshops 8 - 10
Foundries 15 - 30
Garages (Showrooms) 6 - 8
Glasshouses 25 - 60
Gymnasiums 6 min
Hairdressing Salons 10 - 15
Hospitals - Sterilising 15 - 25
- Wards 6 - 8
Kitchens - Domestic 15 - 20
Commercial 20 -30
Laboratories 6 - 15
Launderettes 10 - 15
Laundries 10 - 30
Lavatories 6 - 15
Lecture theatres 5 - 8
Libraries 3 - 5
Living rooms 3 - 6
Mushroom Houses 6 - 10
Offices 6 - 10
Paint shops (not cellulose) 10 - 20
Photo & X-ray darkrooms 10 - 15
Public house bars 10 - 15
Recording studios 10 - 12
Recording Control rooms 15 - 25
Restaurants 8 - 12
Schoolrooms 5 - 7
Shops and Showrooms 8 - 15
Shower baths 15 - 20
Stores & warehouses 3 - 6
Swimming baths 10 - 15
Toilets 6 - 10
Utility rooms 15 - 20
Welding shops 15 - 30

Exhaust Temperature Calculation – Heat Load

This calculation is based on taking the ambient conditions of the air, calculating the discharge temperature of the evaporative cooler, and then performing an energy balance to achieve a target exhaust temperature from the building.

Ambient temperature Ti °C
Ambient RH RH%
Discharge temperature from cooler Tc °C
Heat generated in building H KW
Target Air temperature out Te °C
Volumetric flow rate of Air V m 3/s

The temperature of the air Tc leaving the evaporative cooler is found by using the psychrometric chart using an adiabatic cooling efficiency of 85%.

The flow rate of air required to meet the target exhaust temperature is then given by:

V=1.28H/(Te-Tc)

This flow rate can then be used to select the type and numbers of coolers.

Example.

A target temperature of 27 °C is required in a building which has a heat gain of 100KW. The external conditions are 30 °C 35%RH.

Step 1 – Calculate the cooler discharge temperature using the ambient conditions:

At 30 °C 35%RH and a pad efficiency of 85% the discharge temperature from the evaporative cooler is 20.7 °C

Step 2 – Calculate the air flow rate required to maintain the target temperature:

Te=20.7°c

Tc=27.0 °C

H = 100KW

V = 0.78x100/(27.0-20.7)=78/6.3=12.4m 3/s

Therefore a total flow rate of 12.4m 3/s is required

Step 3 – Calculate the number of coolers required:

An ECP16000@150Pa delivers 14,000 / 3600 = 3.8m 3/s

Number of coolers 12.4 / 3.8 = 3.4 = 4 coolers

Exhaust Temperature Calculation – Heat Load with Stratification

The previous method can be further refined if a temperature stratification exists. If the degree of stratification is known then a thermal balance can be done to maintain a temperature at the lowest level in the building.

Ambient temperature Ti °C
Ambient RH RHa%
Heat generated in building H KW
Target Air temperature at lower level Tl °C
Temperature differential Td
Temperature at high level (exhaust) Th
Heat generated in building H KW
Volumetric flow rate of Air V m 3/s

The temperature of the air Tc leaving the evaporative cooler is found by using the psychrometric chart using an adiabatic cooling efficiency of 85%.

The flow rate of air required to meet the target exhaust temperature is then calculated using the following equation:

Air flow = 0.78xH/(Tl+Td-Ti)

Example

A target temperature of 24 °C is required in a building which has a heat load of 150KW. The ambient conditions are 32 °C 30%RH. There is a 5 °C temperature stratification in the building.

Step 1 – Calculate the discharge temperature of the evaporative cooler. (See Section 17)

At 32 °C 30%RH and a pad efficiency of 85% the discharge temperature from the evaporative cooler is 21.2 °C

Step 2 – Calculate the flow rate of air

V=(0.78 x 150)/(24+5-21.2)=117/7.8=15.0m 3/s

Step 3 – Calculate the number of coolers require

An ECP16000@150Pa delivers 14,000/3600=3.8m 3/s

Number of coolers 15.0 / 3.8 = 3.9 = 4 coolers

Spot Cooling

Spot cooling is calculated based on principles similar to the air changes per hour method. The output from a cooler together with the discharge height of the air can be used to understand the air changes per hour in a given area. A design can then be done to reflect the operating conditions.

A given volume of air discharged at a given height will give the diameter of a circular area from a given target number of air changes per hour to the following calculation.

Height of discharge of air H m
Diameter of circular area D m
Cooler flow rate V m 3/hr
Air Changes per hour A

A = (4 x V)/(3.142xDxDxH)

D = sqrt((4xV)/(3.142xAxH))

Example

What diameter circle will achieve 25 air changes per hour with an ECP16000 producing 14000 m 3/hr with a plenum discharge height of 3.5m?

V=14000

H = 3.5

A = 25

D = sqrt(4x14000)/(3.142x25x3.5) = sqrt (56000/274.9) = sqrt (203.7) = 14.2m

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Evaporatif klima'nın kazandırdıkları

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Evaporative Cooling

Procool specialise in providing and supporting professional factory cooling, production space cooling, warehouse cooling and cooling for commercial premises at affordable prices, and without any of the issues that make conventional air conditioning impractical for these spaces.

Natural Air Cooling Process

Using a natural process called evaporative cooling, fresh air is cooled and cleaned for a fraction of the price of air conditioning, and with a massively reduced impact on your energy bills and carbon footprint.

Evaporative Cooling -30 Million Installations

Even with an estimated 30 million installations worldwide, evaporative cooling is still relatively new to the UK. However, with its high efficiency, affordable prices and ability to work without the need to seal your factory or change your working practices, it is fast becoming the standard method for cooling factories and storage spaces to make working conditions safe and acceptable, and to protect stock and processes.

Air Cooling Process Comparison Chart

	Evaporative Cooling	Air Conditioning	Forced Ventilation
Installation Cost	£6,000	£18,000	£4,500.00
Energy Costs (hot summer day)	£0.14 per hour	£0.81 per hour	£0.10 per hour
Average Temperature Drop Inside the Room	8 deg C at design conditions, more as it gets hotter outside	8 deg C at design conditions, less as it gets hotter outside	Reduces temperature to a few degrees above outside temperature in ideal conditions, never better
Carbon Emmisions	1.5 tonnes per year	12 tonnes per year	1.5 tonnes per year

Air Cooling Processes

The chart below compares evaporative cooling with other air-cooling processes, based on a 20m x 20m factory space. For further details or your FREE on-site 'proof of concept' demonstration, please contact us here.

	Permanently Installed Evaporative Cooling	Air Conditioning	Forced Ventilation	Hired Mobile Evaporative Coolers
Energy Costs (hot summer day)	£0.14 per hour	£0.81 per hour	£0.10 per hour	£0.14 per hour, plus ventilation costs
Energy Costs (average summer day)	£0.11 per hour	£0.49 per hour	£0.10 per hour	£0.11 per hour, plus ventilation costs
Carbon Emissions	1.5 tonnes per year	12 tonnes per year	1.5 tonnes per year	1.5 tonnes per year
Installation Cost	�6,000.00	�18,000.00	£4,500.00	�2,500.00 every year, plus forced ventilation costs to make it work
Average Temperature Drop Inside the Room	8 deg C at design conditions, more as it gets hotter outside	8 deg C at design conditions, less as it gets hotter outside	Reduces temperature to a few degrees above outside temperature in ideal conditions, never better	8 deg C if placed in a doorway with extract, typically zero or even a temperature increase if placed close to the work area
Air Distribution	Can be the whole room or just problem areas	Whole room. Cold spots can develop close to outlets	Can be the whole room or just problem areas	Very poor �is unlikely to deliver any cooling to the problem area, if placed near a door as required
Effect of Increasing Outside Temperature	More cooling with no limit	Less cooling, and then complete failure	Still very little temperature reduction. Often turned off in the afternoons to stop it blowing hot air over people and processes	More cooling ONLY if placed outside, otherwise zero cooling
Fresh Air	100% filtered fresh air	Recirculated stale air. Fresh air should always be introduced, increasing installation costs and reducing performance	100% fresh air. Can be filtered at extra cost	Needs fresh air to work, but there is rarely enough available where the cooling is needed
Operating Conditions	Doors and windows can be left open. Through traffic has no effect	Doors and windows must be closed to create an enclosed environment	Doors and windows can be left open	Must be placed close to a source of 100% fresh air
Effect on Humidity	Neutral when properly designed. Can be used to humidify if required without losing the cooling effect	Reduces humidity at the expense of cooling effect	Unpredictable, but never better than ambient	Rapidly humidify the room and stop cooling altogether
Environmental Impact	Low carbon emissions. Low energy use. Zero CFC/HCFC usage. Plain water to drain	High carbon emissions. Requires CFC/HCFC management and possibly monitoring. Compressor contains oil requiring specialist disposal	Very high carbon emissions and energy usage per deg C temperature reduction	Low carbon emissions, but in most applications energy is used for little or no benefit

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(Evaporative cooling) Evaporatif Soğutma

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EVAPORATIVE COOLING

How an Evaporative Cooler Works

In the Arizona desert in the 1920s, people would often sleep outside on screened-in sleeping porches during the summer. On hot nights, bed sheets or blankets soaked in water would be hung inside of the screens. Whirling electric fans would pull the night air through the moist cloth to cool the room.

That concept, slightly more refined, became the evaporative coolers that to this day provide a low-cost, low-technology alternative to refrigerated air conditioning.

An evaporative cooler produces effective cooling by combining a natural process - water evaporation - with a simple, reliable air-moving system. Fresh outside air is pulled through moist pads where it is cooled by evaporation and circulated through a house or building by a large blower. As this happens, the temperature of the outside air can be lowered as much as 30 degrees.

Probably because evaporative coolers add moisture to the air and blow it around, they are sometimes knows as "swamp coolers." Evaporative coolers can work wonderfully well, provided the outside air they are drawing in is dry and desert-like. As the humidity increases, however, the ability for them to cool the air effectively decreases. Simply put, swamp coolers were not designed to work in swamp-like conditions.

Air conditioning, on the other hand, became popular because of its ability to cool the air, no matter what the humidity might be. Even on humid days, room and central air conditioners can lower the temperature to a thermostatically controlled temperature. They also use as much as four times as much electricity than swamp coolers do, and they are more expensive to install and maintain. Air conditioners can require ozone-damaging refrigerants, and they recirculate the same air over and over.

Fairly popular in desert areas, swamp coolers will work fine most of the time in California's more humid climates. Sacramento, for example, averages about 30 percent humidity on a typical hot summer afternoon, still dry enough for evaporative cooling to work effectively. Despite the potential, however, Dick Bourne of the Davis Energy Group estimates that fewer than five percent of California homes and businesses use evaporative cooling.

Want to Know Why Evaporation Lowers Temperature?

The process of evaporation happens all the time. Our bodies, for example, perspire in hot weather; through evaporation the sweat dries and drops our body temperature.

Whenever dry air passes over water, some of the water will be absorbed by the air. That's why evaporative cooling naturally occurs near waterfalls, at rivers, lakes and oceans. The hotter and drier the air, the more water that can be absorbed. This happens because the temperature and the vapor pressure of the water and the air attempt to equalize. Liquid water molecules become gas in the dry air, a process that uses energy to change the physical state. Heat moves from the higher temperature of the air to the lower temperature of the water. As a result, the air is cooler. Eventually the air becomes saturated, unable to hold more water, and evaporation ceases.

Animation provided by AdobeAir, Inc.

How Evaporative Cooling Works

An evaporative cooler is essentially a large fan with water-moistened pads in front of it. The fan draws warm outside air through the pads and blows the now-cooled air throughout the house.

The pads can be made of wood shavings - wood from aspen trees is a traditional choice - or other materials that absorb and hold moisture while resisting mildew. Aspen wood pads, also called excelsior, need to be replaced every season or two, and generally cost $20 to $40 for a set.

Small distribution lines supply water to the top of the pads. Water soaks the pads and, thanks to gravity, trickles through them to collect in a sump at the bottom of the cooler. A small recirculating water pump sends the collected water back to the top of the pads.

Since water is continually lost through evaporation, a float valve - much like the one that controls the water in a toilet tank - adds water to the sump when the level gets low. Under normal conditions, a swamp cooler can use between 3 to 15 gallons of water a day.

A large fan draws air through the pads, where evaporation drops the temperature approximately 20 degrees. The fan then blows this cooled air into the house.

Small units can be installed in a window, blowing cooled air directly into a room. Larger units can blow air into a central location, or the air can travel through ductwork to individual rooms.

Normal air conditioning is a closed system, taking air from inside a house and recycling it. For air conditioning to function properly, doors and windows should be closed. Evaporative cooling, however, takes air from outside the house. For evaporative cooling to work properly, the cooled outside air must be allowed to escape. By choosing which doors or windows in your home you leave open, you can to help direct the flow of cooled air to areas where it is needed.

How Well Do Swamp Coolers Cool?

The temperature of air coming out of an evaporative cooler obviously depends on the temperature and the humidity of the air going in. This chart from the .....shows that an evaporative cooler can deliver comfortable air under a wide variety of typical summertime temperature and humidity ranges.

In addition to the dropping the temperature of the air, evaporative cooling offers an additional cooling benefit. The constant movement of the air created by the blower - the cooling breeze it creates, if you will - makes the occupants of a room feel 4 to 6 degrees cooler than the actual temperature. This is the same effect you feel when you turn on a ceiling fan or a simple window fan. For this reason, the "effective temperature" created by an evaporative cooler will feel 4 to 6 degrees cooler than temperatures shown on the chart.

An added benefit of evaporative cooling is that it works best in the hottest time of the day. As the temperature outside increases as the sun climbs, the humidity normally drops. In the early morning, for example, the temperature may be 70 degrees, with a relative humidity of 60 percent. By mid-afternoon, when the temperature has climbed to 90 degrees, the humidity may well have dropped to 30 percent - conditions that make evaporative cooling work more effectively.

how to choose the right-sized evaporative cooler

For a swamp cooler to effectively cool, it must be the proper size for the job. A small portable unit, for example, will not adequately cool a large-sized room.

While the output of air conditioners are rated in BTUs (British Thermal Units), evaporative coolers are rated by CFMs (the cubic feet per minute of air that the cooler can blow into your home).

Whether it is for a single room or a whole house, there is a simple formula for determining the proper size of swamp cooler you need. Figure the cubic feet of space you want to cool, and then divide that number by two. The quotient will give you the CFM rating for the proper-sized swamp cooler.

For example, if you have a 1,500 square foot home with 8 foot-high ceilings:

1,500 x 8 = 12,000 cubic feet 12,000 % 2 = 6,000 CFM needed

Benefits of Evaporative Cooling

• Thanks to a new awareness of energy efficiency, evaporative coolers are achieving a new popularity. Remember, swamp coolers use as much as 75 percent less electricity as air conditioning does. The Sacramento Municipal Utility District estimates the electricity savings at approximately $150 a year. For hotter desert climates, the savings can be much more.


• Because the technology is simpler, an evaporative cooler costs about half as much as an air conditioner that will cool the same sized area. Some California utilities, such as PG&E, also offer rebates up to $300 to electricity customers who install whole-house evaporative systems. For perspective, a quick check of the internet in July 2001, found units capable of cooling 750 square feet that were priced as low as $275. Installation costs of swamp coolers are comparable to air conditioning units.


• Evaporative coolers operate on 120-volt electricity, which means they don't need special high-amperage circuits like many air conditioners do. A swamp cooler can be plugged into a nearby outlet.


• Many people appreciate the fact that evaporative cooling adds moisture to the air, which helps to keep wood furniture and fabrics from drying out. The moist pads through which the outside air flows are also fairly efficient air filters, trapping some dust and pollen. Since the pads are continually wetted, trapped particles are flushed out and trapped in the bottom of the cooler.


• Air conditioning works best when the windows are closed, since interior air is cooled and recirculated. Because swamp coolers cool outside air and blow it into the house, however, to work effectively they need at least one window open. The cooled outside air vents through open windows or doors, pushing out hot inside air and any smoke, odors and pollution that may be present. With evaporative cooling, a complete air change in a home occurs every one-to-three minutes. This flow of fresh air means that evaporative coolers can be operated without using the water pump to replace warm stale air with cooler nighttime air, much like a whole house fan does. That's an added benefit.


• Small evaporative coolers can be often placed in windows, much like a window air conditioner. This requires very little installation. Larger units usually require ducts to distribute the air, but these can be an existing forced air duct system in the house.


• For the most part, evaporative cooling doesn't require as much ductwork as air conditioning. For a newly installed system, a short duct can direct the cooled air to a central point in the house. From there, air can be directed through the various rooms by simply opening and closing doors and windows to allow the cooled air to flow.

Drawbacks to Evaporative Cooling

The main drawback of swamp coolers is that they depend on dry outside air to operate effectively. This is usually not a problem for most of California, which has a desert or Mediterranean climate. On hot, muggy days in the summer, however, swamp coolers will blow hot, humid, soggy air into the house. If the humidity stays high for several days, the moist pads that make the evaporative cooler work can begin to smell, and the musty odor can be blown into the house.

Unfortunately for parts of the California desert and for much of the desert Southwest, July and August constitute the rainy season, when monsoon storms sweep north from Baja California. With high temperatures accompanied by high humidity, these months can be the least favorable for swamp coolers.

Evaporative cooling requires water to keep pads wet - a consideration in some areas, especially in drought years. Water consumption can run from three to 15 gallons a day, depending on the size of the swamp cooler and whether or not the water is collected and pumped through the pads more than once. In some areas, discarded water from the unit can be an environmental concern.

Evaporative coolers can be hooked up to existing forced air duct systems. Because the air delivered by an evaporative system will be warmer than the air supplied by an air conditioner, however, evaporative coolers need to produce more air flow. That means the duct system may have to be larger to handle the volume of air and to effectively cool the house.

What's New

Two stage evaporative coolers have been developed that pre-cool air before it goes through the moistened pad. The new coolers are reported to be as effective as air conditioning, but their initial cost is high - around $5,000 for a whole house system, approximately the same as air conditioning. The price may come down as more such systems are sold, but for the time being two-stage systems are hard to find.

Evaporative coolers are now on the market that use photovoltaic panels to create the electricity used to run the blower and the water pump. For hot, desert areas, the combination of evaporative cooling and solar power are a perfect match: the afternoon, when the most solar energy is available, is also the hottest part of the day, when cooling is most needed. And since swamp coolers use a fraction of the energy of air conditioners, PV cells can provide enough electricity to run the system effectively.

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Neden (Evaporative Cooling )Evaporatif Soğutma

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Evaporative cooling has gained rapid acceptance because the process relies solely on water evaporation with extremely low energy consumption to produce a significant amount of cooling.

Evaporative cooling will generally pay for itself (including installation) in just a few seasons. This equates to a valuable investment for consumers, who on the average, own the same home for 5-6 years. Also, the low cost of maintaining this equipment is an added advantage to the end user.

Evaporative cooling makes sense as add-on equipment to complement existing refrigerated air systems. Installing an evaporative cooler significantly reduces the amount of time that mechanical refrigeration is needed in a given season and the associated higher cost of operation.

December 1, 1999

Phoenix Manufacturing Inc. (PMI), takes Dual Air Mobile!

Respecting the contractor and the limited amount of time they have for new product presentations, the Dual Air Plus Heat unit can be brought to them.

This specially engineered trailer contains a fully operational demonstration unit that can be rolled out on it�s own mobile cart for viewing and shows. During outside expositions the 10 foot square awning, which is also stored in the trailer, can be assembled in a matter of minutes. Wholesale distributors and contractors can call to request a �road show� presentation.

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