Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B39/00—Evaporators; Condensers
  • F25B39/04—Condensers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B39/00—Evaporators; Condensers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28B—STEAM OR VAPOUR CONDENSERS
  • F28B1/00—Condensers in which the steam or vapour is separate from the cooling medium by walls, e.g. surface condenser
  • F28B1/02—Condensers in which the steam or vapour is separate from the cooling medium by walls, e.g. surface condenser using water or other liquid as the cooling medium
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28C—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA COME INTO DIRECT CONTACT WITHOUT CHEMICAL INTERACTION
  • F28C1/00—Direct-contact trickle coolers, e.g. cooling towers
  • F28C1/14—Direct-contact trickle coolers, e.g. cooling towers comprising also a non-direct contact heat exchange
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28C—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA COME INTO DIRECT CONTACT WITHOUT CHEMICAL INTERACTION
  • F28C1/00—Direct-contact trickle coolers, e.g. cooling towers
  • F28C1/16—Arrangements for preventing condensation, precipitation or mist formation, outside the cooler
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D3/00—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium flows in a continuous film, or trickles freely, over the conduits
  • F28D3/02—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium flows in a continuous film, or trickles freely, over the conduits with tubular conduits
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D7/08—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being otherwise bent, e.g. in a serpentine or zig-zag
  • F28D7/082—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being otherwise bent, e.g. in a serpentine or zig-zag with serpentine or zig-zag configuration
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F25/00—Component parts of trickle coolers
  • F28F25/02—Component parts of trickle coolers for distributing, circulating, and accumulating liquid
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2339/00—Details of evaporators; Details of condensers
  • F25B2339/04—Details of condensers
  • F25B2339/041—Details of condensers of evaporative condensers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2339/00—Details of evaporators; Details of condensers
  • F25B2339/04—Details of condensers
  • F25B2339/046—Condensers with refrigerant heat exchange tubes positioned inside or around a vessel containing water or pcm to cool the refrigerant gas
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B2339/00—Details of evaporators; Details of condensers
  • F25B2339/04—Details of condensers
  • F25B2339/047—Water-cooled condensers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F25/00—Component parts of trickle coolers
  • F28F2025/005—Liquid collection; Liquid treatment; Liquid recirculation; Addition of make-up liquid
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
  • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
  • Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Definitions

• An improved evaporative condenser and evaporative condensation process are disclosed for use in refrigeration and air-conditioning systems.
• the condenser and process can be employed with both chemical refrigerants (e.g. hydrofluorocarbons) and natural refrigerants (e.g. hydrocarbons (such as propane & isobutane), C0 2 , ammonia, etc).
• chemical refrigerants e.g. hydrofluorocarbons
• natural refrigerants e.g. hydrocarbons (such as propane & isobutane), C0 2 , ammonia, etc).
• plan area of the condensing coils is matched to the plan area of the drift eliminators to ensure constant air flow rate and airstream velocity through the evaporative condenser.
• heat exchange efficiency is limited by the velocity of air that flows over the condensing coils.
• the velocity of air is in turn limited by the ability of the drift eliminators to remove free water from the air passing therethrough.
• such removed water is recycled for reuse in wetting the condensing coils.
• any water that passes with the air flowing through the drift eliminators to atmosphere may contain bacteria, such as legionella, hence the requirement to remove as much free water from the airstream as possible.
• evaporative condenser for use in a refrigeration or air- conditioning system.
• the evaporative condenser as disclosed herein can condense chemical refrigerants (e.g. hydrofluorocarbons, hydrochlorofluorocarbons,
• perfluorocarbons such as propane & isobutane, C0 2 , ammonia, etc.
• natural refrigerants e.g. hydrocarbons such as propane & isobutane, C0 2 , ammonia, etc.
• the evaporative condenser as disclosed herein also comprises a mechanism for wetting the one or more condensing coils (e.g. by spraying them with water).
• the evaporative condenser as disclosed herein further comprises drift eliminators arranged to remove free water from an airstream that has flowed past the one or more condensing coils and wetting mechanism.
• the divergent zone is able to cause the airstream leaving the condensing coil zone to decelerate. This means that the velocity of air passing over the condensing coils can be increased, relative to the velocity of air passing through the drift eliminators. This higher velocity can help to reduce fouling of the tube.
• each of the one or more condensing coils may employ stainless steel tube (e.g. 304 or 316 stainless steel of 4.76 - 31.8 mm outside diameter and 0.5 - 1.6 mm thickness). The use of 304 stainless steel can offer better
• 316 stainless steel can offer better corrosion resistance.
• Such tube material can perform favourably in comparison to a known condensing coil tube of galvanized mild carbon steel.
• the use of very small diameter tube can be suitable for certain small-scale applications.
• stainless steel tube material i.e. due to corrosion/chemical resistance, increased refrigerant pressure capacity, etc
• a natural refrigerant such as a propane and/or isobutane hydrocarbon, C0 2 , ammonia, etc, to be employed.
• the divergent part of the zone can be configured to cause the airstream to decelerate in a gradually decreasing manner.
• the divergent zone can comprise a hollow frustum (hollow air plenum) through which the airstream flows.
• a hollow frustum may be located on the air exit side of the condensing coil plenum.
• the divergent frustum when the condensing coil plenum is of circular section, the divergent frustum each comprise a conical frustum, or a square-to-circular frustum-like prism; when the condensing coil plenum is of square section, the divergent frustum may comprise a square frustum; etc.
• the condenser may comprise an air inlet chamber located at an air entry side of the condensing coil zone.
• the mechanism for wetting the one or more condensing coils may comprise one or more spray nozzles.
• the spray nozzles may be arranged with respect to the divergent zone to spray water onto the one or more condensing coils in a direction that is counter to the airstream flow through the one or more condensing coils.
• the spray nozzles may be arranged in the divergent zone, and may spray the water generally as a liquid cone into the condensing coil zone.
• the mechanism for wetting the one or more condensing coils may comprise water distribution channels, such as those with serrated edges, internal slots, etc.
• the condenser can comprise a water collection zone (e.g. located at a base of an air inlet chamber).
• the collection zone can collect water that has passed through condensing coil zone.
• the condenser can further comprise a recycling system for recycling the collected water to the wetting mechanism, to maximize condenser efficiency.
• the recycling system can comprise a pump for pumping the collected water via pipework to the wetting mechanism.
• an offtake pipe can extend from the base of the air inlet chamber to the pump, and a delivery pipe can extend from the pump outlet to the wetting mechanism (e.g. to spray nozzle, distribution pipework, etc).
• an evaporative condenser that comprises the collection zone for collecting water that has passed through condensing coil zone, and that comprises the heat exchanger through which the collected water is passed prior to recycling it to the wetting mechanism, and through which the condensed refrigerant is passed to exchange heat with the recycled collected water.
• Also disclosed herein is an evaporative condensation process forming part of a refrigeration or air-conditioning cycle.
• the process comprises passing refrigerant through one or more condensing coils.
• the process also comprises wetting the one or more condensing coils with water.
• the process further comprises passing an airstream over the one or more wetted condensing coils whereby refrigerant is caused to condense within the coils, and whereby a portion of the water is caused to evaporate into the airstream.
• the process additionally comprises eliminating water that is present in the airstream leaving the one or more condensing coils.
• the process is conducted such that the velocity of the airstream leaving the one or more condensing coils is caused to decelerate prior to eliminating the water that is present in the airstream.
• Also disclosed herein is an evaporative condensation process in which the water that passes through the one or more condensing coils is collected and recycled to wet the one or more condensing coils with water. Further, in such a process, heat can be exchanged between the condensed refrigerant and the collected water, prior to recycling it to wet the one or more condensing coils.
• the refrigerant condensed in the one or more condensing coils can comprise a natural refrigerant (e.g. a hydrocarbon such as propane and/or isobutane, C0 2 , ammonia, etc) or a chemical refrigerant (e.g. a
• Figure 1 shows cross-sectional side schematic of an evaporative condenser having a condensing coil zone in which one or more condensing coils are arranged, and a divergent zone extending away from the condensing coil zone;
• Figures 3A and 3B respectively show cross-sectional and side schematics of an evaporative condenser having a convergent-divergent zone in which one or more condensing coils are arranged;
• Figure 5 is a graph showing C0 2 and water temperature profiles in accordance with the Examples.
• Figure 6 is a graph showing C0 2 heat capacity profile in accordance with the Examples.
• Figure 7 is a graph showing water flow down the tube bundle in accordance with the Examples.
• Figure 8 is a graph showing overall heat transfer coefficient & pressure loss in accordance with the Examples.
• Figure 9 is a graph showing a heat rejection profile based on a commercially available transcritical C0 2 compressor at 5°C sat. suction, with 5 K useful suction superheat and 5°C C0 2 liquid temperature, in accordance with the Examples;
• Figure 10 is a graph showing performance of a commercially available transcritical C0 2 compressor at 50 Hz. 30 kW/27.2 m 3 /h, in accordance with the Examples; and Figure 1 1 is a graph showing the variation in COPs of NH 3 , R22 R507A, Propane and R134a with Saturated Condensing Temperature, in accordance with the Examples.
• Evaporative condenser embodiments designated 10 and 100 are respectively shown in Figure 1 & 2 and Figures 3 A & 3B.
• the evaporative condensers embodiments 10 and 100 are able to employ both chemical and natural refrigerants (as set forth above).
• Figures 4 to 11 relate to embodiments described in the Examples.
• the preferred evaporative condenser 10 of Figures 1 and 2 comprises two or more nested condensing coil bundles 12 that have flowing (for condensing) therewithin the selected refrigerant of the system.
• the condensing coil bundles 12 are arranged in a condensing coil zone in the form of a rectangular airflow plenum 13.
• the spray nozzles 14 are arranged to spray water onto the condensing coil bundles 12 in a direction that is counter to the airstream flow therethrough as shown.
• the evaporative condenser 10 also comprises a fan arranged in a fan housing at an upper end of the condenser.
• a fan 1 18 arranged in a fan housing 120 located at an uppermost end of the condenser (see Figure 3A).
• the fan causes air to be drawn via an air inlet 21 into an air inlet chamber 22 that is arranged towards the lower end of the condenser 10.
• the airstream A enters at a volumetric flow rate of e.g. 8.1 m /s, first passing through mesh filters and then into the air inlet chamber 22, before it is caused by the fan to flow up to and through the condensing coil bundles 12.
• the air pressure differential can be maintained by the fan at e.g. 160Pa.
• the evaporative condenser 10 further comprises drift eliminators 30 which are arranged within the condenser adjacent to an upper end thereof.
• the drift eliminators 30 remove free water from the airstream once it has flowed past the condensing coil bundles 12 and spray nozzles 14.
• the fan is operated such that the airstream A is already at a higher velocity at the condensing coil bundles 12 relative to the drift eliminators 30. Having flowed past the condensing coil bundles 12, the airstream A flows into the divergent airflow plenum 40, passing through the water cones 16.
• the airflow is able to decelerate to an acceptable velocity before it reaches and passes through the drift eliminators 30.
• the evaporative condenser 10, and in particular, the divergent airflow plenum 40 is configured such that this velocity is at a level whereby an environmentally acceptable minimum amount of free water in the airstream can be eliminated therefrom.
• the airflow rate at the drift eliminators 30 can decelerate to approximately 3.5 m/s.
• the embodiment of Figures 1 & 2 does not employ a convergent airflow zone. Rather, the airflow velocity from the air inlet chamber 22, and through the condensing coil bundles 12, is approximately 5 m/s, until the airflow reaches the divergent airflow plenum 40, whereupon the airflow gradually decelerates to approximately 3.5 m s at the drift eliminators 30.
• the condensing coil bundles 1 12 are arranged in the intermediate airflow zone 1 13.
• the configuration of these zones is such that the airstream A flows through and is accelerated in the convergent airflow zone 135 to the condensing coil bundles 1 12 located in the intermediate airflow plenum 113 (e.g. to approximately 5 m/s).
• the airstream A flows into the divergent airflow zone 140, passing through the water cone 16, and decelerating before reaching the drift eliminators 130.
• the drift eliminators 130 are arranged immediately at the air exit of the divergent airflow plenum 140.
• the convergent airflow zone 135 is configured to cause the airstream A to accelerate, such as in a gradually increasing manner.
• the divergent airflow zone 140 is configured to cause the airstream to decelerate, such as in a gradually decreasing manner.
• the airflow rate in the intermediate airflow zone 1 13 is approximately double at ⁇ 5 m/s, (i.e. about 45% higher than) the 3.5 m/s air velocity through the drift eliminators.
• the condensing coil bundle represents the single-most expensive component of the condenser.
• a more expensive and/or stronger material such as stainless steel tube, can be used to form the coil bundle 12, 112.
• the result is longer coil life, less corrosion and, if desired, thinner wall material for the tube in the coil bundle.
• the coil bundle 12, 1 12 can comprise stainless steel tube, such as 304 or 316 stainless steel of 4.76 - 31.8 mm outside diameter and 0.5 - 1.6 mm thickness.
• Such tube is observed to perform well in comparison to known condensing coil tube of galvanized mild carbon steel.
• the corrosion and chemical resistance, as well as increased refrigerant pressure capacity, that is provided by such stainless steel tube materials also allows a natural refrigerant, such as a propane and/or isobutane hydrocarbon, C0 2 , ammonia, etc, to be employed in the evaporative condenser 10, 100.
• Another consequence of the increased airflow rate over the condensing coils is that an increased flow of refrigerant can be passed through the condensing coil bundle 12, 1 12 because the greater air velocity is able to bring about condensation of a relatively greater amount of refrigerant.
• the condenser 10 also comprises a water collection zone in the form of a basin 50 located at a base of (i.e. adjacent to) the air inlet chamber 22.
• the basin 50 collects excess spray water that has passed through or from condensing coils.
• the condenser 10 additionally comprises a recycling system for recycling the collected water to the distributor tube 15 for feeding to the spray nozzles 14.
• the recycling system comprises a pump 52 for pumping the collected water via pipework to the distributor tube 15.
• the pump 52 draws water out of the basin 50 via an offtake pipe 54.
• a delivery pipe section 56 then extends from the pump outlet to connect with the distributor tube 15.
• the recycling system also comprises water make-up 58 (e.g. at 383 kg/h) for maintaining a predetermined amount of water in the basin 50 for effective operation of the evaporative condenser.
• make-up water can include a supply of water that has been eliminated (captured) by the drift eliminators 30.
• the condensed refrigerant in the condenser tubes can also be passed via refrigerant delivery pipe 62 to and through the heat exchange unit 60 to exchange heat with the recycled water from the basin 50.
• the relatively cool basin water can sub-cool the condensed refrigerant, for example, from 30°C to around 26.5°C. This can further improve the operational efficiency of the refrigerating system.
• the refrigerant (e.g. C0 2 ) leaving the heat exchange unit 60 as the stream 64 can be at a sub-cooled temperature (e.g. around 26.5°C).
• Non-limiting examples of the present condenser and process will now be provided in order to illustrate the theoretical basis of the condenser and process, and to better understand the condenser and process in operation.
• a design model for the application to subcritical C0 2 condensing of evaporative condensers such as those depicted in Figures 1 to 3, was developed. More specifically, the benefits of applying evaporative condensing techniques for the condensation of subcritical C0 2 were examined. Such benefits included lower design pressures compared to trans-critical operations, lower energy consumption, and lower running and operating costs. It was noted that hot gas defrosting could also become a standard feature of subcritical C0 2 refrigeration plant operations.
• ammonia can be condensed at 30°C in an evaporative condenser with an entering air wet bulb temperature of 24°C.
• an evaporative condenser for subcritical C0 2 condensing at 30°C i.e. 1.1 K below the critical point
• an examination of average climate conditions revealed that much of Europe, including Spain, Italy, Greece and Turkey, has a climate where evaporative condensers may be applied for the condensing of C0 2 at subcritical conditions at a condensing temperature of 30°C or lower 100% of the time in many locations.
• the only location in Europe where the 5% design Wet Bulb temperature incidence exceeded 24° C was Adana in Turkey (where the 1 and 2.5% wet bulb incidence design levels are at 26° C).
• the 1% wet bulb design incidence is at 25° C, but the 2.5% and 5% wet bulb design incidence levels are at 24° C.
• the next highest 1% wet bulb design incidence level of 24° C occurred at Gibraltar, Barcelona, Valencia, Milan, Istanbul and Izmir.
• summer design C0 2 exit temperatures from an air cooled gas cooler were higher than the critical temperature, and this resulted in the compressors needing to operate at a pressure of 90 bar or higher to ensure a reasonable COP.
• the summer design COPs of trans-critical C0 2 compressors were generally lower than those of air cooled HFC or evaporatively cooled ammonia systems.
• FIG. 4 shows a schematic flow sheet of an evaporative condenser that will now be further described.
• water was recycled over the tube bank, so that spray water temperature was the same as the basin water temperature.
• Figures 5 and 6 show C0 2 and water temperature profiles.
• the shape of the C0 2 temperature profile ( Figure 5) was a surprise - it was much flatter than expected.
• the C0 2 vapour temperature only reduced from 32 to 30°C at interval number 29. This was a consequence of the very high heat capacity just above 30°C ( Figure 6).
• the model predicted that 67% of exchanger surface would be needed for sensible cooling.
• Figure 7 shows the water flow down the tube bundle. Another surprise was that water did not evaporate to air at the top of the bundle. Here, water temperature was low though rising, and water contacted air with a humidity ratio higher than the humidity ratio at the air-water interface, so some condensation occurred and water flow increased.
• Figure 8 illustrates the effects of changes in heat capacity, density, viscosity and thermal conductivity with temperature on overall heat transfer coefficient and pressure loss over each solution interval. Interval zero was where the hot discharge gas enters.
• the COP ranged from 6.27 at +30°C Saturated Condensing Temperature (SCT) to 18.0 at an SCT of + 16°C at a Saturated Suction Temperature (SST) of +10°C.
• SCT Saturated Condensing Temperature
• SST Saturated Suction Temperature
• a +10°C SST would allow an Evaporating Temperature (ET) of +11°C with a suction pressure drop corresponding to 1 K boiling point suppression.
• 1 1°C was noted as a reasonably efficient evaporating temperature for direct cooling of Air Conditioning (AC) air, allowing a relatively large diffusion in air temperature across the cooling coil, thus limiting the volume of air which would need to be circulated, and thereby reducing fan energy consumption and the resulting parasitic heat load. This in turn would lead to a reduction in the required energy input into the compressor thereby lifting the overall energy efficiency of the system as a whole.
• AC Air Conditioning
• AC compressors could act also as parallel compressors for refrigeration duties at -5°C SST, such as maintaining chill storage temperatures at around 0°C and high stage duties for two stage C0 2 systems applied to cold storage and blast freezing applications.
• COP curve 3 ranged from 4.7 to 7.88 at an SST of -5°C at SCTs ranging from +30 to +16°C and a virtual gas cooler exit of +5°C.
• COP curve 4 showed the COP ranging 4.45 to 7.04 with a virtual gas cooler exit of +10°C, and SST of ⁇ 5°C and the SCT ranging from +30 to +16°C. It was noted that this could be improved with a Suction Heat Exchanger (SHEX) in the compressor suction to bring the performance closer to curve 3. Effect of ambient Wet Bulb temperature on condenser performance
• FIG. 4 shows the general details on C0 2 , air and water.
• the Effect of ambient Wet Bulb temperature on condenser performance is shown in the results set forth in the following table:
• the high ⁇ / ⁇ ratio of C0 2 allowed high mass fluxes in the condenser circuits giving high rates of heat transfer, allowing fewer longer circuits, which also made for more economical manufacture of the tube bundle.
• ammonia mass fluxes in evaporative condensers range from about 25 to 40 kg/m2.s and are frequently lower than 25.
• the pressure drop was a concern with ammonia condensers, as excessive pressure drop in an ammonia evaporative condenser lifts the discharge pressure, and thus the Saturated Condensing Temperature (SCT), resulting in increased energy consumption.
• SCT Saturated Condensing Temperature
• the calculated leaving air Dry Bulb Temperature is 29.3°C at 100% RH and hence the leaving Wet Bulb Temperature was also 29.3°C. This was only 0.7°K lower than the SCT of 30°c. This was possible because the top tubes were at a temperature of 77°C and the high proportion of sensible superheat ensured that there was a high leaving approach TD available of 47.7°K. It was noted that this was not possible in ammonia evaporative condensers, where minimum leaving temperatures approaches between the ammonia SCT and the leaving Wet Bulb are rarely less than 3K and not less than 2.5K at design conditions. Little airflow also resulted in minimum fan energy consumption.
• Plain or finned tube Plain Condenser exit air dry bulb 28.8 Plain tube OD 15.88 mm Condenser exit air RH 100.1 % Tube ID 13.48 mm Condenser air pressure drop 102 P

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Central Air Conditioning (AREA)

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• 2015
  • 2015-05-13 US US15/310,001 patent/US20170153048A1/en not_active Abandoned
  • 2015-05-13 CN CN201580025168.0A patent/CN106461297A/zh active Pending
  • 2015-05-13 AU AU2015258758A patent/AU2015258758A1/en not_active Abandoned
  • 2015-05-13 WO PCT/AU2015/000277 patent/WO2015172180A1/en active Application Filing
  • 2015-05-13 JP JP2017512071A patent/JP2017519182A/ja active Pending
  • 2015-05-13 CA CA2947774A patent/CA2947774A1/en not_active Abandoned
  • 2015-05-13 KR KR1020167033827A patent/KR20170005047A/ko unknown
  • 2015-05-13 EP EP15792017.4A patent/EP3146279A4/de not_active Withdrawn
• 2016
  • 2016-11-17 ZA ZA2016/07964A patent/ZA201607964B/en unknown

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