Evaporative Cooling Applicability in the Middle East · Evaporative Cooling Applicability in the...

Evaporative Cooling Applicability in the Middle EastOxycom Fresh Air BV∗

April 14th, 2015

AbstractOxycom developed various evaporative cooling solutions,either as standalone configurations or as combinations oftechnologies, to cover the entire climate of the MiddleEast. Standalone Oxyvap direct evaporative cooling ispreferred in areas having low absolute humidity, two-stage Oxyvap or standalone Oxycell indirect evaporativecooling in areas having low to moderate absolute humid-ity and Oxyvap-based condenser pre-cooling or Oxycell-based hybrid cooling in areas having low to high absolutehumidity.

1 Introduction1.1 Company overviewOxycom is a Dutch company specialized in the devel-opment and production of products and components foradiabatic cooling, indirect evaporative cooling, dew pointcooling, air humidification and heat recovery.Oxycom developed, engineered and manufactures the

Oxycell Indirect Evaporative Heat Exchanger and theOxyvap Direct Evaporative Cooling pad.

The Oxycell is the base of highly efficient all seasonfresh air systems that provide dew point cooling, indir-ect evaporative cooling, heat recovery and ventilation.The Oxyvap is the base of highly efficient cooling-onlysystems that provide direct evaporative cooling, humid-ification and ventilation.

∗Oxycom Fresh Air BV - P.O. Box 212, NL-8100 AE Raalte -Phone: +31(0)572 349 400 - E-mail: [email protected]

1.2 Scope of the paperThe Middle East consumes large amounts of electrical en-ergy to power conventional vapor compression air condi-tioning systems for residential, commercial and industrialpurposes, mainly originating from fossil fuels [1]. Oxy-com uses water instead, one of nature’s most powerfulrefrigerants (R718) [2], to cool air in an environmentallyfriendly matter.

Evaporating water at a rate of 1 L/h generates 695 Wof cooling power [3], whereas conventional air condition-ing systems typically require as much as 250−300 W ofelectrical power to achieve the same [4]. Desalination ofwater at at rate of 1 L/h typically requires only 4 W ofelectrical power [5].

This paper shows the applicability of Oxycom’s evap-orative cooling technologies and technology combina-tions, based on outdoor air conditions in a range of majorcities throughout the Middle East.

2 Technology overview2.1 IntroductionOxycom developed several evaporative cooling techno-logies and technology combinations, each with its ownapplicability region.

• Standalone Oxyvap: suitable for any outdoor tem-perature and outdoor absolute humidity up to 12g/kg.

• Two-stage Oxyvap: suitable for any outdoor tem-perature and outdoor absolute humidity up to 16g/kg.

• Standalone Oxycell: suitable for any outdoor tem-perature and outdoor absolute humidity up to 16g/kg.

1

(XRD-Q-007-2) Evaporative Cooling Applicability in the Middle East

• Oxycell-based hybrid cooling: suitable for any out-door temperature and humidity.

• Oxyvap-driven condenser pre-cooling: suitable forany outdoor temperature and humidity.

2.2 Standalone Oxyvap

The Oxyvap is a direct evaporative cooling pad,that adiabatically cools air towards its wet bulb temper-ature, typically achieving a 90% saturation efficiency.Its modular design enables it to be used for any airflow,while the frontal air velocity is typically 1−3 m/s.

2.3 Two-stage Oxyvap

The two-stage Oxyvap is an Oxyvap-based coolingconfiguration, that uses an additional air-to-water heatexchanger to enhance its performance. Chilled waterfrom the Oxyvap is fed to the heat exchanger to pre-cooloutdoor air before it enters the Oxyvap pad, that is thenfed with water returning from the heat exchanger.Since it is a closed system, the cooling process as a

whole will be adiabatic, but the combination of the pre-cooling process and the recirculation of water betweenthe components will lead to a vertical temperature gradi-ent in the air leaving the Oxyvap pad.

The upper half of the supply air will have a higherenthalpy than the intake air, whereas the lower half willhave a lower enthalpy. When the upper half of the airis discarded, the lower half can be used as supply air,reaching an average temperature below the initial wetbulb temperature, while less moisture is added comparedto traditional adiabatic cooling.

2.4 Standalone Oxycell

The Oxycell is a counter-flow indirect evaporativeheat exchanger in which air in the secondary channel(work air) is adiabatically cooled and humidified, herebyextracting heat from air in the primary channel (processair). This principle is referred to as Indirect EvaporativeCooling (IEC).

Dew Point Cooling (DPC) is a special applicationof the Oxycell IEC principle, in which part of the cooledprimary outlet air (typically 35−40%) is branched offand used as secondary inlet air, where it is cooledadiabatically, hereby extracting heat from the primaryair stream. Ideally, primary air can be cooled down toits dew point temperature, while maintaining a constantabsolute humidity.

Whether DPC or IEC is the preferred cooling methoddepends on various parameters, such as the outdoor airconditions, heat load and fan configuration.

2


2.5 Oxycell-based hybrid cooling

The hybrid configuration is based on the OxycellIEC principle. In practice, the Oxycell IEC coolsoutdoor air (flowing through the primary channel) downto about a degree above the physical limit, i.e. thewet bulb temperature of the secondary inlet air, whilemaintaining a constant absolute humidity.When humid outdoor air conditions do not allow for

sufficient cooling from the Oxycell itself, the evaporatorcoil from a conventional vapor compression air condi-tioning system may be used to cool and dehumidify pre-cooled air from the Oxycell to the desired supply air con-ditions. The condenser coil is placed downstream of thesecondary (wet) channel of the Oxycell. Generally, thisair is cooler than the outdoor air, leading to an increasein compressor efficiency.

Annual savings are typically 50% compared to existingstandalone conventional air conditioning systems.

2.6 Oxyvap-based condenser pre-cooling

In conventional air conditioning technology, a com-pressor is used to compress the gaseous coolant beforeit loses its heat by condensation in the condenser coil.When using the Oxyvap to pre-cool the outdoor air thatis supplied to the condenser coil, the coolant is ableto condense at a lower temperature, hereby decreasingthe work that has to be done by the compressor and

consequently increasing its efficiency.

3 Climate data3.1 IntroductionTypically, throughout the Middle East, the outdoor tem-perature can exceed 40 °C or even 50 °C for a substan-tial amount of hours per year. The absolute humidity,on the other hand, depends strongly on the geograph-ical position. Rather than the temperature, evaporativecooling performance is mainly determined by the abso-lute humidity. To illustrate the applicability of Oxycom’sevaporative cooling technologies and technology combin-ations in the Middle East, 35 major cities in 15 countrieshave been selected, of which hourly climate data between2007 and 2014 has been analysed [6].

The graphs below show per city which absolutehumidity values occur during a year, divided in 2 g/kgintervals. A distinction into absolute humidity categorieshas been made based on the highest absolute humiditythat occurs, with the exception of the 175 most humidhours, such that it covers 98% of the year, in accordancewith ASHRAE climatic design guidelines [7].

Absolute humidity categories:

• Low: up to 12 g/kg.

• Low to moderate: up to 16 g/kg.

• Low to high: to above 16 g/kg.

3.2 Low absolute humidity

535

3932

3439

809

45 0 0 0 0 0 0 00

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Dura

tion [

hours

/year]

Outdoor absolute humidity [g/kg]

Shiraz (Iran)

3


305

3759

3292

1084

304

16 0 0 0 0 0 00

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4500

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Dura

tion [

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/year]


Tabuk (Saudi Arabia)

164

2438

2949

2056

1073

791 0 0 0 0 0

0

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4500

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Dura

tion [

hours

/year]


Ankara (Turkey)

745

35453424

825

205

14 3 0 0 0 0 00

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4500

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Dura

tion [

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/year]


Tehran (Iran)

567

3625

3037

1100

425

4 1 1 0 0 0 00

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4500

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Dura

tion [

hours

/year]


Mashhad (Iran)

748

2724

2925

1620

710

30 2 1 0 0 0 00

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4500

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Dura

tion [

hours

/year]


Tabriz (Iran)

442

4011

2042

1334

910

17 1 3 0 0 0 00

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4500

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Dura

tion [

hours

/year]


Sana'a (Yemen)

4


58

2560

3976

1482

572

90 22 0 0 0 0 00

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Dura

tion [

hours

/year]


Riyadh (Saudi Arabia)

139

1623

3895

2118

825

14120 0 0 0 0 0

0

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Dura

tion [

hours

/year]


Baghdad (Iraq)

36

1676

3426

2816

699

76 24 6 0 0 0 00

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1000

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2000

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4500

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Dura

tion [

hours

/year]


Aswan (Egypt)

713

4102

2281

1016

470

108 67 2 0 0 0 00

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1000

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4500

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Dura

tion [

hours

/year]


Medina (Saudi Arabia)

107

1350

3845

1928

1085

355

910 0 0 0 0

0

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Dura

tion [

hours

/year]


Amman (Jordan)

206

1389

25252423

1710

371

1306 0 0 0 0

0

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1000

1500

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4500

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Dura

tion [

hours

/year]


Gaziantep (Turkey)

5


3.3 Low to moderate absolute humidity

21

935

2130

2700

2135

607

225

8 0 0 0 00

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Dura

tion [

hours

/year]


Izmir (Turkey)

0155

1429

2642 2607

1427

468

31 0 0 0 00

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Dura

tion [

hours

/year]


Luxor (Egypt)

13

857

2235

1906

1700

1088

720

20134 6 0 0

0

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4500

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Dura

tion [

hours

/year]


Istanbul (Turkey)

28

1186

2727

2531

1398

462

26490 58 14 1 2

0

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Dura

tion [

hours

/year]


Mosul (Iraq)

72

1033

2880

2491

1422

407297

63 53 21 19 30

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Dura

tion [

hours

/year]


Basrah (Iraq)

286

28532934

1072

890

331214

87 50 20 16 60

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4500

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Dura

tion [

hours

/year]


Kuwait City (Kuwait)

6


3.4 Low to high absolute humidity

3

195

1238

2456

2133

956 1013

535

219

11 0 00

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Dura

tion [

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/year]


Nicosia (Cyprus)

28

514

1934

1513

1332

949

1300

774

380

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Dura

tion [

hours

/year]


Cairo (Egypt)

1

185

776

1691

1874

1054

1287

1005

716

15515 0

0

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Dura

tion [

hours

/year]


Beirut (Lebanon)

18

1192

1653

1118

1370

865

1429

671

320

10419 0

0

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22+

Dura

tion [

hours

/year]


Baku (Azerbaijan)

0 5

211

1164

2775

1144 11251255

894

16122 3

0

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1000

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4500

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Dura

tion [

hours

/year]


Alexandria (Egypt)

18

1058

2791

1935

1221

670582

190 15076 39 29

0

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1000

1500

2000

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4000

4500

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Dura

tion [

hours

/year]


Dammam (Saudi Arabia)

7


88

411

1263

2022

1765

855 916

573 517

197 1502

0

500

1000

1500

2000

2500

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3500

4000

4500

0 ─

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Dura

tion [

hours

/year]


Antalya (Turkey)

195339 300

375

764

980

1245

941

2071

1238

306

50

500

1000

1500

2000

2500

3000

3500

4000

4500

0 ─

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22+

Dura

tion [

hours

/year]


Salalah (Oman)

3

256

1166

2052 2011

10981004

586

287114 151

31

0

500

1000

1500

2000

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3000

3500

4000

4500

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Dura

tion [

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/year]


Al Ain (United Arab Emirates)

0 0 38

345

1125

1403

2315

1878

1051

318231

55

0

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2000

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4000

4500

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Dura

tion [

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Mecca (Saudi Arabia)

0 28170

374

10611193

2030

1546

1212

617

432

98

0

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4500

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Dura

tion [

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Jeddah (Saudi Arabia)

0 19

223

1139

1983

1460

1264

852 851

334418

216

0

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4500

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Dura

tion [

hours

/year]


Manama (Bahrein)

8


0165

521

849

1847

14801357

691559 507 472

312

0

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3500

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4500

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Dura

tion [

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/year]


Abu Dhabi (United Arab Emirates)

397

401

694

16271547

1469

792

585475

615456

0

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1000

1500

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4500

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Dura

tion [

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/year]


Dubai (United Arab Emirates)

3162

743

1158

1607

1094 1164

654770

456378

572

0

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1000

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2000

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4500

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Dura

tion [

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Doha (Qatar)

0 28

230

504

1079

14321310

769

580411

851

1566

0

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1000

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4500

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Dura

tion [

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/year]


Muscat (Oman)

4 Applicability4.1 IntroductionThe outdoor absolute humidity classification determinesthe preferred technology or combination of technologies.

• Low: standalone Oxyvap.

• Low to moderate: two-stage Oxyvap or standaloneOxycell.

• Low to high: Oxyvap-based condenser pre-coolingor Oxycell-based hybrid cooling.

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4.2 Low absolute humidity

Tehran

ShirazTabuk

Mashhad

Ankara

Tabriz

Sana'a

RiyadhAswan

Baghdad

Gaziantep

Amman

Medina

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4.3 Low to moderate absolute humidity

Izmir

Luxor

Istanbul

Mosul

Basrah

Kuwait City

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4.4 Low to high absolute humidity

Cairo

Baku

Alexandria

Dammam

Antalya

Salalah

Al Ain

Jeddah

Manama

Abu Dhabi

Dubai

Doha

Muscat

Mecca

Nicosia

Beirut

5 SummaryCategory of outdoor Number of Geographical Preferred Alternativeabsolute humidity cities* location technology technologyLow 13 Desert or arid Standalone Oxyvap Condenser pre-cooling

desertlike inland or two-stage Oxyvapor standalone Oxycell

Low to moderate 6 Mainly between Two-stage Oxyvap Condenser pre-coolingcoast and inland or standalone Oxycell

Low to high 16 Mainly coastal Condenser pre-coolingor hybrid cooling

*Out of a total of 35 analysed cities in the Middle East.

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References[1] Glada Lahn, Paul Stevens and Felix Preston,

Chatham House, the Royal Institute of InternationalAffairs, Saving Oil and Gas in the Gulf (2013).

[2] American Society of Heating, Refrigerating andAir-Conditioning Engineers, 2009 ASHRAE Hand-book−Fundamentals (SI), Chapter 29−Refrigerants(2009).

[3] American Society of Heating, Refrigerating andAir-Conditioning Engineers, 2009 ASHRAE Hand-book−Fundamentals (SI), Chapter 1−Psychromet-rics (2009).

[4] SKM Air Conditioning Equipment, PACX SeriesPackaged Air Conditioners (Range 6 TR to 50 TR),Refrigerant - R134a, Bulletin # 051/2007 (2007).

[5] DESWARE, Encyclopedia of Desalination and Wa-ter Resources, Energy Requirements of DesalinationProcesses, http://www.desware.net/desa4.aspx.

[6] The Weather Channel, LLC, Weather Underground,http://www.wunderground.com.

[7] American Society of Heating, Refrigerating andAir-Conditioning Engineers, 2009 ASHRAE Hand-book−Fundamentals (SI), Chapter 14−ClimaticDesign Information (2009).

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