Evaporative Cooling Applicability in the Middle East

Transcription

1 Evaporative Cooling Applicability in the Middle East Oxycom Fresh Air BV April 14th, 215 Abstract Oxycom developed various evaporative cooling solutions, either as standalone configurations or as combinations of technologies, to cover the entire climate of the Middle East. Standalone Oxyvap direct evaporative cooling is preferred in areas having low absolute humidity, twostage Oxyvap or standalone Oxycell indirect evaporative cooling in areas having low to moderate absolute humidity and Oxyvap-based condenser pre-cooling or Oxycellbased hybrid cooling in areas having low to high absolute humidity. 1 Introduction 1.1 Company overview Oxycom is a Dutch company specialized in the development and production of products and components for adiabatic cooling, indirect evaporative cooling, dew point cooling, air humidification and heat recovery. Oxycom developed, engineered and manufactures the Oxycell Indirect Evaporative Heat Exchanger and the Oxyvap Direct Evaporative Cooling pad. The Oxycell is the base of highly efficient all season fresh air systems that provide dew point cooling, indirect evaporative cooling, heat recovery and ventilation. The Oxyvap is the base of highly efficient cooling-only systems that provide direct evaporative cooling, humidification and ventilation. 1.2 Scope of the paper The Middle East consumes large amounts of electrical energy to power conventional vapor compression air conditioning systems for residential, commercial and industrial purposes, mainly originating from fossil fuels [1]. Oxycom uses water instead, one of nature s most powerful refrigerants (R718) [2], to cool air in an environmentally friendly matter. Evaporating water at a rate of 1 L/h generates 695 W of cooling power [3], whereas conventional air conditioning systems typically require as much as 25 3 W of electrical power to achieve the same [4]. Desalination of water at at rate of 1 L/h typically requires only 4 W of electrical power [5]. This paper shows the applicability of Oxycom s evaporative cooling technologies and technology combinations, based on outdoor air conditions in a range of major cities throughout the Middle East. 2 Technology overview 2.1 Introduction Oxycom developed several evaporative cooling technologies and technology combinations, each with its own applicability region. Standalone Oxyvap: suitable for any outdoor temperature and outdoor absolute humidity up to 12 g/kg. Two-stage Oxyvap: suitable for any outdoor temperature and outdoor absolute humidity up to 16 g/kg. Standalone Oxycell: suitable for any outdoor temperature and outdoor absolute humidity up to 16 g/kg. Oxycom Fresh Air BV - P.O. Box 212, NL-81 AE Raalte - Phone: +31() info@oxy-com.com 1

2 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East Oxycell-based hybrid cooling: suitable for any outdoor temperature and humidity. Oxyvap-driven condenser pre-cooling: suitable for any outdoor temperature and humidity. 2.2 Standalone Oxyvap The upper half of the supply air will have a higher enthalpy than the intake air, whereas the lower half will have a lower enthalpy. When the upper half of the air is discarded, the lower half can be used as supply air, reaching an average temperature below the initial wet bulb temperature, while less moisture is added compared to traditional adiabatic cooling. 2.4 Standalone Oxycell The Oxyvap is a direct evaporative cooling pad, that adiabatically cools air towards its wet bulb temperature, typically achieving a 9% 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 Oxycell is a counter-flow indirect evaporative heat exchanger in which air in the secondary channel (work air) is adiabatically cooled and humidified, hereby extracting heat from air in the primary channel (process air). This principle is referred to as Indirect Evaporative Cooling (IEC). The two-stage Oxyvap is an Oxyvap-based cooling configuration, that uses an additional air-to-water heat exchanger to enhance its performance. Chilled water from the Oxyvap is fed to the heat exchanger to pre-cool outdoor air before it enters the Oxyvap pad, that is then fed 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 precooling process and the recirculation of water between the components will lead to a vertical temperature gradient in the air leaving the Oxyvap pad. Dew Point Cooling (DPC) is a special application of the Oxycell IEC principle, in which part of the cooled primary outlet air (typically 35 4%) is branched off and used as secondary inlet air, where it is cooled adiabatically, hereby extracting heat from the primary air stream. Ideally, primary air can be cooled down to its dew point temperature, while maintaining a constant absolute humidity. Whether DPC or IEC is the preferred cooling method depends on various parameters, such as the outdoor air conditions, heat load and fan configuration. 2

3 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East 2.5 Oxycell-based hybrid cooling consequently increasing its efficiency. 3 Climate data The hybrid configuration is based on the Oxycell IEC principle. In practice, the Oxycell IEC cools outdoor air (flowing through the primary channel) down to about a degree above the physical limit, i.e. the wet bulb temperature of the secondary inlet air, while maintaining a constant absolute humidity. When humid outdoor air conditions do not allow for sufficient cooling from the Oxycell itself, the evaporator coil from a conventional vapor compression air conditioning system may be used to cool and dehumidify precooled air from the Oxycell to the desired supply air conditions. The condenser coil is placed downstream of the secondary (wet) channel of the Oxycell. Generally, this air is cooler than the outdoor air, leading to an increase in compressor efficiency. Annual savings are typically 5% compared to existing standalone conventional air conditioning systems. 2.6 Oxyvap-based condenser pre-cooling 3.1 Introduction Typically, throughout the Middle East, the outdoor temperature can exceed 4 C or even 5 C for a substantial amount of hours per year. The absolute humidity, on the other hand, depends strongly on the geographical position. Rather than the temperature, evaporative cooling performance is mainly determined by the absolute humidity. To illustrate the applicability of Oxycom s evaporative cooling technologies and technology combinations in the Middle East, 35 major cities in 15 countries have been selected, of which hourly climate data between 27 and 214 has been analysed [6]. The graphs below show per city which absolute humidity values occur during a year, divided in 2 g/kg intervals. A distinction into absolute humidity categories has been made based on the highest absolute humidity that occurs, with the exception of the 175 most humid hours, such that it covers 98% of the year, in accordance with 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 Shiraz (Iran) In conventional air conditioning technology, a compressor is used to compress the gaseous coolant before it loses its heat by condensation in the condenser coil. When using the Oxyvap to pre-cool the outdoor air that is supplied to the condenser coil, the coolant is able to condense at a lower temperature, hereby decreasing the work that has to be done by the compressor and

4 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East Tabuk (Saudi Arabia) Mashhad (Iran) Ankara (Turkey) Tehran (Iran) Tabriz (Iran) Sana'a (Yemen)

5 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East Riyadh (Saudi Arabia) Medina (Saudi Arabia) Baghdad (Iraq) Aswan (Egypt) Amman (Jordan) Gaziantep (Turkey)

6 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East 3.3 Low to moderate absolute humidity Mosul (Iraq) Izmir (Turkey) Basrah (Iraq) Luxor (Egypt) Kuwait City (Kuwait) Istanbul (Turkey)

7 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East 3.4 Low to high absolute humidity Baku (Azerbaijan) Nicosia (Cyprus) Alexandria (Egypt) Cairo (Egypt) Dammam (Saudi Arabia) Beirut (Lebanon)

8 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East Antalya (Turkey) Mecca (Saudi Arabia) Salalah (Oman) Al Ain (United Arab Emirates) Jeddah (Saudi Arabia) Manama (Bahrein)

9 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East Abu Dhabi (United Arab Emirates) Muscat (Oman) Dubai (United Arab Emirates) Doha (Qatar) Applicability 4.1 Introduction The outdoor absolute humidity classification determines the preferred technology or combination of technologies. Low: standalone Oxyvap. Low to moderate: two-stage Oxyvap or standalone Oxycell. Low to high: Oxyvap-based condenser pre-cooling or Oxycell-based hybrid cooling. 9

10 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East 4.2 Low absolute humidity Ankara Gaziantep Tabriz Tehran Mashhad Amman Baghdad Tabuk Shiraz Aswan Medina Riyadh Sana'a 1

11 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East 4.3 Low to moderate absolute humidity Istanbul Izmir Mosul Basrah Luxor Kuwait City 11

12 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East 4.4 Low to high absolute humidity Antalya Baku Nicosia Beirut Alexandria Cairo Dammam Jeddah Mecca Manama Doha Abu Dhabi Dubai Al Ain Muscat Salalah 5 Summary Category of outdoor Number of Geographical Preferred Alternative absolute humidity cities* location technology technology Low 13 Desert or arid Standalone Oxyvap Condenser pre-cooling desertlike inland or two-stage Oxyvap or standalone Oxycell Low to moderate 6 Mainly between Two-stage Oxyvap Condenser pre-cooling coast and inland or standalone Oxycell Low to high 16 Mainly coastal Condenser pre-cooling or hybrid cooling *Out of a total of 35 analysed cities in the Middle East. 12

13 (XRD-Q-7-2) Evaporative Cooling Applicability in the Middle East References [1] Glada Lahn, Paul Stevens and Felix Preston, Chatham House, the Royal Institute of International Affairs, Saving Oil and Gas in the Gulf (213). [2] American Society of Heating, Refrigerating and Air-Conditioning Engineers, 29 ASHRAE Handbook Fundamentals (SI), Chapter 29 Refrigerants (29). [3] American Society of Heating, Refrigerating and Air-Conditioning Engineers, 29 ASHRAE Handbook Fundamentals (SI), Chapter 1 Psychrometrics (29). [4] SKM Air Conditioning Equipment, PACX Series Packaged Air Conditioners (Range 6 TR to 5 TR), Refrigerant - R134a, Bulletin # 51/27 (27). [5] DESWARE, Encyclopedia of Desalination and Water Resources, Energy Requirements of Desalination Processes, [6] The Weather Channel, LLC, Weather Underground, [7] American Society of Heating, Refrigerating and Air-Conditioning Engineers, 29 ASHRAE Handbook Fundamentals (SI), Chapter 14 Climatic Design Information (29). 13