WO2016074077A1 - Systèmes et procédés d'échange d'énergie - Google Patents

Systèmes et procédés d'échange d'énergie Download PDF

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Publication number
WO2016074077A1
WO2016074077A1 PCT/CA2015/051161 CA2015051161W WO2016074077A1 WO 2016074077 A1 WO2016074077 A1 WO 2016074077A1 CA 2015051161 W CA2015051161 W CA 2015051161W WO 2016074077 A1 WO2016074077 A1 WO 2016074077A1
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WIPO (PCT)
Prior art keywords
lamee
unit
desiccant liquid
air
supply
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PCT/CA2015/051161
Other languages
English (en)
Inventor
Robert W. Besant
Carey James SIMONSON
Richard William EVITTS
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University Of Saskatchewan
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Publication of WO2016074077A1 publication Critical patent/WO2016074077A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
    • F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
    • F24F3/14—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification
    • F24F3/147—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification with both heat and humidity transfer between supplied and exhausted air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F12/00—Use of energy recovery systems in air conditioning, ventilation or screening
    • F24F12/001—Use of energy recovery systems in air conditioning, ventilation or screening with heat-exchange between supplied and exhausted air
    • F24F12/002—Use of energy recovery systems in air conditioning, ventilation or screening with heat-exchange between supplied and exhausted air using an intermediate heat-transfer fluid
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F3/00—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems
    • F24F3/12—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling
    • F24F3/14—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification
    • F24F2003/1458—Air-conditioning systems in which conditioned primary air is supplied from one or more central stations to distributing units in the rooms or spaces where it may receive secondary treatment; Apparatus specially designed for such systems characterised by the treatment of the air otherwise than by heating and cooling by humidification; by dehumidification using regenerators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F2203/00—Devices or apparatus used for air treatment
    • F24F2203/10—Rotary wheel
    • F24F2203/1032—Desiccant wheel
    • 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
    • F28D21/00—Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00
    • F28D21/0015—Heat and mass exchangers, e.g. with permeable walls
    • 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]
    • Y02B30/56—Heat recovery units

Definitions

  • HVAC heating, ventilation and/or air conditioning
  • the exchanger includes a housing having a front and a back.
  • a plurality of panels forming desiccant channels extend from the front to the back of the housing. Air channels are formed between adjacent panels. The air channels are configured to direct an air stream in a direction from the front of the housing to the back of the housing.
  • a desiccant inlet is provided in flow communication with the desiccant channels.
  • a desiccant outlet is provided in flow communication with the desiccant channels.
  • the desiccant channels are configured to channel desiccant from the desiccant inlet to the desiccant outlet in at least one of a counter-flow or cross- flow direction with respect to the direction of the air stream.
  • the energy exchange system includes a supply air flow path, an exhaust air flow path, an energy recovery device disposed within the supply and exhaust air flow paths, and a supply conditioning unit disposed within the supply air flow path.
  • the supply conditioning unit may be downstream from the energy recovery device.
  • a method of conditioning air includes introducing outside air as supply air into a supply air flow path, pre-conditioning the supply air with an energy recovery device, and fully-conditioning the supply air with a supply conditioning unit that is downstream from the energy recovery device.
  • Figure 1 is a schematic view of a first example of an energy exchange system for conditioning air in an interior space of a structure
  • Figure 2 is a schematic view of a second example of an energy exchange system for conditioning air in an interior space of a structure
  • Figure 3 is a detailed schematic view of an auxiliary loop of the systems of Figure 1 or Figure 2.
  • This problem may be reduced by selecting a salt solution or mixture of salt solutions that is well suited to the operating conditions under which the exchanger will operate during each day and month of the year. This problem may also be reduced by selecting semipermeable membranes that are most suitable for integration into the design of heat and water vapor transfer exchangers. Furthermore, this problem may be reduced by using system designs and controls that are well suited to avoid crystallization problems. Moreover, this problem may be reduced by sizing and operating a regenerating exchanger at conditions where the salt solution does not, at any point in the exchanger or the system, approach the salt solution saturation conditions too closely for the design flux of heat and water vapor.
  • crystallization of the salt will generally occur at the air-liquid interface or meniscus in those regions of the exchanger and at adjacent membrane surface roughness imperfections where the liquid salt concentration is close to saturation conditions, the desiccant solution temperature is low, the temperature of the salt solution is much higher than the air temperature, and the flux of heat and water vapor out of the liquid interface is large.
  • Predicting the exact conditions for crystallization in a membrane exchanger may be difficult because there are uncertainties in fluid and crystallization properties, and there are many operating conditions and properties that must be known. As well, the water purity in the desiccant solution may be high to avoid hard water salt depositions on heated exchanger surfaces. Such deposits may also degrade the performance of exchangers. Extensive testing and data collection may be necessary to provide a complete set of operating conditions for each membrane and inlet fluid properties, and each of their uncertainties that will avoid crystallization and blockage of membrane exchangers used for moisture removal from salt solutions near saturation conditions.
  • AHRI Standard 1060 test condition for air-to-air heat/energy exchangers may not be enough; the HVAC system has to perform well at the typical most extreme outdoor and indoor conditions for each application (i.e. when the risk of crystallization is greatest). It is only when the operating conditions are at their extreme loading conditions that the load capacity of an HVAC system may be determined for any application.
  • Various salt solutions have somewhat similar thermodynamic properties and phase diagrams. Depending on the concentration of the salt, they may freeze at temperatures below 0 °C (e.g., LiCI solutions will not freeze above -50 °C for mass concentrations above 20% salt/solution), and they may have vapor pressures in air that will be less than atmospheric pressure unless its temperature is above boiling (100 °C). Between these temperatures, the equilibrium vapor pressures may be nearly, but not exactly, coincident with the relative humidity lines on a psychrometric chart for air and water vapor. Salt solutions at or near thermodynamic equilibrium will not experience nucleation and crystallization unless the salt solution saturation (i.e.
  • C mass concentration of salt in a unit mass of solution and the subscript "s" denotes the salt saturation condition) rises above 1 .0 [i.e. either due to the evaporation of water from an exposed meniscus (or air-liquid interface), or due to the cooling of the interface or other surfaces bounding the desiccant liquid (i.e. as on a heat exchanger surface)].
  • C S C S
  • T temperature
  • one part of the membrane exchanger desiccant liquid may be at very different operating conditions than another part of the exchanger, and the solution phase diagrams and properties superimposed on a psychrometric chart may not be strictly correct (i.e. deviations from equilibrium conditions may be large).
  • nucleation sites for crystallization processes may occur anywhere within a saturated salt solution, but for small flow channels within membrane exchangers, preferred locations are generally at interface locations at air-liquid interfaces or meniscus and solid heat exchanger surfaces where there are finite fluxes of water vapor and heat out of the liquid (unless the solution is simultaneously heated).
  • a nucleation site for instance on the liquid side of a meniscus, it becomes the chemically preferred site for further crystal growth (i.e. the threshold chemical potential for super-saturation and formation of nucleation sites will be slightly higher than the super- saturation needed for continuous growth to the crystal at the site). That is, beyond a certain critical diameter of a spherical nucleated particle size (e.g.
  • Crystallization is a phase change process, so when it occurs, the local temperature of the solution and the crystal tends to decrease slightly and the surrounding concentration of the solution tends to decrease slightly. This decrease in the local temperature and concentration, surrounding the nucleated crystal, generally results in micro- diffusion processes of heat and salt surrounding each nucleated crystal.
  • the crystals formed will generally not be pure salt; rather, they will be salt molecules plus hydrated water molecules (e.g. , for aqueous LiCI, LiCI:H 2 0 will form above 20 °C, and LiCI:2H 2 0 will form below 20 °C).
  • This hydration of water will generally cause the crystal size to increase and alter the local or micro-concentration of salt more below 20 °C than above (i.e. larger crystals below 20 °C may be a consequence).
  • the density of the crystallized salt may be slightly higher than the surrounding solution, surface tension forces tend to hold the nucleated crystals on the meniscus surface and on membrane solid surfaces.
  • surface roughness on the solid surfaces may generally make preferred sites for nucleation to start.
  • LiCI and LiBr salt solutions may be used for most HVAC applications having liquid salt-solution desiccants.
  • LiCI solution and LiBr solution have relatively low saturation curves when superimposed on the psychrometric chart, and may co-exist with air at low relative humidity at equilibrium. That is, air properties anywhere above the LiCI or LiBr saturation curves on the psychrometric chart may be achieved or maintained in buildings using LiCI or LiBr solutions in HVAC systems.
  • Other types of salt solutions that may also be used are mixtures of either LiCI or LiBr, and other salts such as MgCI 2 , CaCI 2 , NaCI, etc.
  • the salt solution conditions inside a semipermeable membrane exchanger may differ from the outdoor or indoor inlet air conditions because there will be heating and cooling, phase change due to evaporation or condensation of water, and perhaps the injection of water or a weak saline solution.
  • the salt solution in exchangers may be close to equilibrium conditions but at high fluxes it may not, and this may cause both the region of hysteresis for crystallization and dissolution of existing crystals and the bounds of uncertainty for the onset or dissolution of crystallization to grow with the mass flux of water vapor and heat flux out of the solution.
  • the slope of the saturation concentration line, dCs/dT will be significantly smaller than any of the corresponding concentration curves, dC/dT, at the same temperature, T, or some constant concentration curves, C, will intersect the saturation curve, Cs, as the temperature of the solution is decreased).
  • a cooling process (with no water vapor transfer) in the liquid may cause some crystallization.
  • This phenomenon may be seen in the phase diagram for an aqueous solution of LiCI, which shows that cooling an initially sub-saturated solution with C>0.3 (30%) will, at equilibrium, eventually cause crystallization. For example, cooling a LiCI solution from an initial temperature of 50 °C and concentration of 40% (i.e.
  • saturation conditions may exist in one part of the flow [e.g., near a heat exchanger (metal or membrane) surface while cooling the solution flow], but not elsewhere in the flow. That is, crystallization may occur on heat exchanger surfaces and within membrane pores. This crystallization, when extensive, may diminish the effectiveness of the exchanger.
  • the heat exchanger may be designed with sufficient surface area so that the heat flux is not too large and the surface temperatures of the exchanger are not too low at any location in the exchanger.
  • dewatering of the salt solution may be done at high temperatures and at a condition where high exchanger water vapor fluxes do not cause crystallization in the membrane pores, and significant surface area blockage, to achieve a high concentration salt solution in a regenerator exchanger, and then this high concentration salt solution may be cooled to a desired inlet temperature to both cool and dehumidify the supply air in the supply air conditioning exchanger.
  • High fluxes of water vapor while the salt solution concentration is in close proximity to the equilibrium saturation concentration (i.e. 1 -S is small) during dewatering or regeneration of the salt solution may increase the risk of crystallization and blockage of the membrane pores.
  • Two exemplary types of HVAC systems may employ permeable membrane exchangers to transfer heat and water vapor between salt solutions and air flows: (1 ) passive energy recovery systems, which recover the available energy from exhaust air and is stored in a solid or liquid and then used to condition or partly condition supply air; and (2) active air-conditioning systems, which employ several devices or components and, through energy transfer from external sources, may be used to condition the inlet air to selected supply air conditions of flow, temperature and humidity.
  • LAMEE counter-cross-flow liquid-to-air membrane energy exchanger
  • RAMEE passive run-around membrane energy exchanger
  • Passive desiccant liquid energy exchange systems may contain only one supply and one exhaust LAMEE unit in its simplest configuration, but it could be designed to handle several exhaust and supply units.
  • the RAMEE system is passive in the sense that, if these exchangers each have an inlet airflow, and a low power pump or pumps are used to circulate the desiccant liquid through these permeable membrane exchangers and the connecting tubing in a closed loop, heat and moisture may be exchanged between the exhaust and the supply airflows coupled by a closed loop desiccant liquid flow.
  • this passive system may not be entirely free of external energy inputs, and there may be a need for some external water injection to avoid crystallization in one of the solution flow exchangers during supply air humidification, but these auxiliary inputs may be relatively small compared to the mass of air circulated and the energy transfer rate between the two airflows [i.e. the coefficient of performance (COP) at design conditions may be high; e.g., COP>40 where COP is defined as the ratio of energy saving rate for the two air flows and the energy input rate for pumps, fans, and controls].
  • COP coefficient of performance
  • these passive systems may be most likely to experience crystallization when the supply inlet air is very dry (Wi ⁇ 3 g/kg) and cold (Ti ⁇ 0.0 °C), and the exhaust air conditions are dry and warm or typical (e.g., W 3 ⁇ 6 g/kg and T 3 «20 °C), and this possibility may increase when the liquid mass circulation rate is low compared to the air mass flow rates (m r * ⁇ 1 .0 or Cr* ⁇ 3.0), the exchanger at risk of crystallization (i.e. the exhaust exchanger) area is significantly smaller than the supply exchanger area, and the temperature of any liquid make-up water or salt solution is low (T H 2o ⁇ 5 °C).
  • Outdoor air conditions will often be dry and cold for many cities, including much of North America. Hourly weather data may be ignored for those conditions when the RAMEE system is not in operation (i.e. when the economizer bypass is used for the airflows because the COP is low and will become less than 1 .0 when the outdoor air conditions are close to the thermal comfort conditions for the building occupants).
  • the economizer cycle i.e. the ventilation air flow may mostly bypass the HVAC system
  • the HVAC system has an appropriate capacity and controls.
  • Cold climates e.g., Saskatoon and Chicago, may have a significant fraction of hours when the humidity ratios, W, are less than 3 g/kg (i.e. a high risk of crystallization region), and other areas may have a significant fraction of hours when 80 to 100% relative humidity for outdoor temperatures above the economizer operating region (e.g., 20 to 25 °C), which is another region of risk for crystallization for air conditioning systems because relatively large moisture content and mass flow rates must be removed from the ventilation air before it is supplied to the occupied space. Below the economizer temperature range region (e.g. , 15 to 20 °C), most cities have significant fractions of hours in the 80 to 100% relative humidity region.
  • the economizer operating region e.g., 15 to 20 °C
  • the passive system may be designed: (1 ) to use relatively pure LiCI or LiBr salt solutions; (2) the selected semipermeable membrane materials used in the LAMEEs should not only have good permeability, heat transfer and strength properties, but also smooth fiber surfaces within the membrane at the air-liquid solution interface; and (3) the surface areas of the membrane in each LAMEE should be large enough to not result in excessive water vapor mass evaporation and heat transfer fluxes.
  • the passive system has a semipermeable membrane exchanger operating in a near steady state condition near the saturation curve (i.e.
  • crystallization blockage may be avoided by: (i) injecting water or a low saturation salt into the exchanger solution upstream of the exchanger (e.g., into the storage tank where it may be fully mixed to avoid the risk of freezing the unmixed salt solution); (ii) increasing the rate of desiccant liquid flow or decreasing the air flow rate (i.e. increasing Cr*); (iii) increasing the inlet desiccant liquid temperature, T
  • FIG. 1 an example of an active energy exchange system is shown generally at reference numeral 100.
  • the system 100 exchanges air between an interior space 102 and an outside 104 of a structure (not shown).
  • dotted lines indicate desiccant liquid flow tubes extending between the numbered components, whereas air flow channels or ducts extending between the numbered components are illustrated to have a finite width. Both show arrow heads to indicate flow direction.
  • the supply LAMEE units 106a, 106b are connected in parallel and are arranged to receive air from the outside 104.
  • the supply LAMEE units 106a, 106b condition the outside air to form supply air, and deliver the supply air to the interior space 102.
  • the supply LAMEE units 106a, 106b are shown to include desiccant liquid inlets 108a, 108b and desiccant liquid outlets 1 10a, 1 10b.
  • An exhaust LAMEE unit 1 12 is arranged to receive air from the interior space 102 to form exhaust air, and deliver the exhaust air from the interior space 102 to the outside 104.
  • the exhaust LAMEE unit 1 12 is shown to include a desiccant liquid inlet 1 14 and a desiccant liquid outlet 1 16.
  • An auxiliary loop 300 fluidly connects the desiccant liquid outlet 1 16 of the exhaust LAMEE unit 1 12 and the respective desiccant liquid inlets 108a, 108b of the supply LAMEE units 106a, 106b.
  • the auxiliary loop 300 includes a regeneration LAMEE unit 302 for regenerating the desiccant liquid circulating in the system 100.
  • Primary and secondary valves 306, 308 control flow of the desiccant liquid through the regeneration LAMEE unit 302.
  • valves 306, 308 are opened and closed, respectively, so that desiccant liquid is permitted to flow from the desiccant liquid outlet 1 16 of the exhaust LAMEE unit 1 12 to the desiccant liquid inlets 108a, 108b of the supply LAMEE units 106a 106b.
  • the valves 306, 308 are closed and opened, respectively, so that the desiccant liquid is guided to flow through the regeneration LAMEE unit 302.
  • the primary and secondary valves 306, 308 may be controlled so that the regeneration LAMEE unit 302 receives only a portion of the flow of desiccant liquid.
  • the auxiliary loop 300 further includes an auxiliary dehumidifier mechanism 304 coupling the regeneration LAMEE unit 302 and the outside 104.
  • the dehumidifier mechanism 304 serves to transfer moisture away from the regeneration LAMEE unit 302, to reduce the water content of the desiccant liquid.
  • the dehumidifier mechanism 304 may be, for example, a desiccant-coated dehumidifier wheel. Exemplary dehumidifier wheels are commercially available from Munters AB, of Kista, Sweden.
  • the system 100 further includes tanks 1 18, 120 and pumps 122, 124a, 124b.
  • a water source 126 is shown connected to the tank 1 18, to selectively increase water content of the desiccant liquid being supplied to the inlets 108a, 108b.
  • the supply LAMEE units 106a, 106b may be placed at selected locations for each room or zone or region within the structure, and the air may be locally circulated through each of the supply LAMEE units 106a, 106b to achieve the desired comfort conditions for the occupants.
  • the conditions of the desiccant liquid in the system 100 may be predetermined and set at selected mechanical rooms near external walls of the structure, so that large ducts and large flow rates of air in the structure may be generally avoided [i.e. ducts may be used for ventilation, and perhaps exhaust air only, and desiccant tubing may be used in a closed loop (or loops) to condition the air in situ].
  • ducts may be used for ventilation, and perhaps exhaust air only
  • desiccant tubing may be used in a closed loop (or loops) to condition the air in situ.
  • outside air or direct heat may be used to heat or cool, and dewater or inject water, as needed for the desiccant liquid.
  • the conditioned desiccant liquid will be pumped to each room LAMEE.
  • the return desiccant liquid flow goes to the mechanical room for conditioning again in a closed loop.
  • the system 100 may be used to maintain in situ occupant comfort conditioning (i.e. both T and W are controlled by the operating conditions for the supply LAMEE units 106a, 106b), and may have many types of applications for buildings new and retrofit, and for applications where cross contamination between exhaust and supply air is not permitted.
  • Conventional HVAC systems may operate at part load conditions for most of the time for building applications in most cities (i.e. the peak load conditions will only occur for a small fraction of the hours per year, but this condition must be satisfied otherwise the inlet air conditions in the building spaces will become uncomfortable for occupants).
  • control of comfort conditions in humid summer conditions is often a problem because, as the cooling load decreases, the on-off cycle time durations shorten because much of the condensed cooling coil water gets recycled back into the supply air. This short-cycle dehumidifying problem may be avoided with the system 100 because it will generally not exhibit any short cycles.
  • the supply air ventilation flow rate may differ from the exhaust flow rate.
  • an economizer cycle may be used to bypass the supply air ventilation flow between the outside 104 and the supply LAMEE units 106a, 106b, and the exhaust flow between the interior space 102 and the exhaust LAMEE unit 1 12, because the outdoor air is close to comfort conditions.
  • the system 100 may modulate the fraction of ventilation and exhaust air bypass to optimize these operating costs.
  • the system 100 has two supply LAMEE units 106a, 106b, one exhaust LAMEE unit 1 12, and one dewatering or regeneration LAMEE unit 302, other arrangements with more of these units may be implemented in other examples.
  • the auxiliary loop may include two or more regeneration LAMEE units, connected in parallel.
  • the auxiliary loop may include two or more exhaust LAMEE units, connected in parallel to one another.
  • Various configurations are possible.
  • FIG. 2 another example of an active energy exchange system is shown generally at reference numeral 200. Reference numerals are repeated in Figures 1 and 2 and in this description to indicate corresponding or analogous elements or steps.
  • the system 200 includes a dehumidifier mechanism 228 arranged between the supply LAMEE unit 206 and the exhaust LAMEE unit 212.
  • the dehumidifier mechanism 228 serves to exchange moisture from the air from the interior space 202 received by the exhaust LAMEE unit 212, and air from the outside 204 received by the supply LAMEE unit 206.
  • the dehumidifier mechanism 228 may be, for example, a desiccant-coated dehumidifier wheel.
  • the regeneration LAMEE unit 302 is shown to include a desiccant liquid inlet 336 and a desiccant liquid outlet 338.
  • the inlet 336 is fluidly connected to the outlet 1 16 of the exhaust LAMEE unit 1 12 ( Figure 1 ), whereas the outlet 338 is fluidly connected to the inlets 108a, 108b of the supply LAMEE units 106a, 106b.
  • the auxiliary loop 300 further includes heat exchangers 310, 312, 314, 316, 318, 320, 322, and a heat pump 324.
  • the heat exchangers 310, 312 may be used to increase the temperature of the desiccant liquid, before it is delivered to the regeneration LAMEE unit 302.
  • the heat exchangers 314, 316, 318 may be used to decrease the temperature of the desiccant liquid, before it is delivered to the supply LAMEE units 106a, 106b.
  • a third valve 326 is shown connecting the heat exchangers 310, 316, and may facilitate a tube-in-tube transfer of heat between the flow of desiccant liquid downstream of the regeneration LAMEE unit 302 and the flow of desiccant liquid upstream of the regeneration LAMEE unit 302.
  • Reference numeral 328 indicates a waste heat sink coupled to the heat pump 324, and a power input, indicated at reference numeral 332, may also be connected to the heat pump 324.
  • reference numeral 330 indicates a waste heat source, which may be derived from within the structure, e.g., from lights, electric motors, and solar energy.
  • a low-temperature heater 334 is also shown connected to the auxiliary dehumidifier mechanism 304, and may be configured to heat the air flow up to, e.g., 100 °C before entering the auxiliary dehumidifier mechanism 304.
  • the desiccant liquid bypasses most of the auxiliary loop 300.
  • the second mode intended for peak summer conditions, by closing the primary valve 306 and opening the secondary valve 308, desiccant liquid is guided by the auxiliary loop 300 through the regeneration LAMEE unit 302.
  • This regeneration process may help to reduce or eliminate the risk of membrane creep caused by pressure differences across the membranes at elevated operating temperatures (e.g., 45 ⁇ T
  • the heat exchangers 310, 312, 314, 316, 318, 320, 322 may each be liquid-to-liquid heat exchangers designed to meet the peak load and achieve a high effectiveness (e.g., ⁇ >80-90%), and the heat pump 324 may be a liquid-to-liquid heat pump having a COP>5, because the auxiliary loop 300 may have a small or moderate temperature range. Also, at part load operating conditions, the full capacity of the regeneration LAMEE unit 302 may not be used because the valves 306, 308 may be coordinated to restrict flow in the auxiliary loop 300.
  • temperature of the desiccant liquid may be reduced using the heat exchangers 314, 316, 318 so that a desired inlet temperature to the supply LAMEE units 106a, 106b is met from the flows in the auxiliary loop 300, controlled via the primary valve 306, while throughout the loop the solution saturation, S, is less than 1 , and upstream of the tank 1 18 the condition is such that (1 -S) «1 (i.e. the final solution saturation is close to but less than 1 everywhere within the heat exchangers 314, 316, 318 where cooling of the solution occurs).
  • the regeneration LAMEE unit 302 will be utilized, and these outdoor conditions may extend over a wide range of psychrometric chart conditions for most cities.
  • part load conditions defined to be the case for summer operations when the energy removal rate is not near its peak value and the flow rate at the regeneration LAMEE unit 302 is less than its peak value
  • the system 100 may require controls for the air flow through each of the LAMEE units and flow of the desiccant liquid, and, at times when an economizer may be used, because the outdoor air temperatures and humidity are close to the supply air set point, then the supply and exhaust air flow may bypass the entire system.
  • the heat pump 324 may be used to condition the desiccant liquid's temperature to a desired set point, with the heat exchanger 318 being the last component of the auxiliary loop 300, which may be used to precisely control the temperature of the desiccant liquid for delivery to the inlets 108a, 108b.
  • the regeneration LAMEE unit 302 may also be used to condition the desiccant liquid's solution concentration to a desired set point, for delivery to the inlets 108a, 108b of the supply LAMEE units 106a, 106b. Thus, crystallization conditions may be avoided in both the exhaust LAMEE unit 1 12 and the regeneration LAMEE unit 302.
  • the supply LAMEE units 106a, 106b may achieve both these functions, but may risk crystallization within its membranes unless the desiccant liquid's solution concentration at the inlets 108a, 108b is sufficiently low, because water will be transferred from the desiccant liquid to the supply air.
  • the water source 126 may be used to selectively add water to the tank 1 18.
  • the heat pump 324 may be used to preheat the desiccant liquid, via the heat exchanger 322 upstream of the inlets 108a, 108b.
  • the auxiliary loop 300 required for summer operations, may not be generally used, except as a backup. Without any waste heat, heat may be directly added to the solution upstream of the inlets 108a, 108b.
  • the heat exchanger 320 is shown coupled to the heat pump 324, which may have the waste heat energy sink 328 with a significant potential for heat removal, including, e.g. , ground water, river water, lake water, etc.
  • the heat exchanger 322 may be an auxiliary heat source, e.g., provided by a boiler and fired by natural gas. During summer operations, the heat exchangers 320, 322 may be bypassed, e.g., by closing the primary valve 306.
  • the inlet and internal solution temperature may exceed occupant comfort temperatures (i.e. 45 °C or higher) for the solution regeneration process in the regeneration LAMEE unit 302 during the highest summer load conditions for outdoor air, so that the solution saturation ratio, S, will not be too close to 1 (e.g., 1 -S>0 everywhere in the regeneration LAMEE unit 302), and so the risk of crystallization during regeneration of the solution will be avoided even though the salt solution concentration will increase for solution flow through the regeneration LAMEE unit 302.
  • occupant comfort temperatures i.e. 45 °C or higher
  • S solution saturation ratio
  • heat may be supplied to the regeneration LAMEE unit 302 via the air supplied from the auxiliary dehumidifier mechanism 304 using the heat exchanger 314, the waste heat source 330, and/or the heater 334, while the outlet air relative humidity is very low (e.g., less than 10%).
  • the systems described herein may avoid many uncertainties that are inherent in other active systems, which dewater the desiccant liquid at lower temperatures, and at or near the saturation line.
  • the desiccant liquid may be monitored for temperature and concentration prior to the supply LAMEE units, with proper controls, so that the desiccant liquid does not approach super-saturation anywhere in the loop or in the LAMEE units.
  • the systems described herein may employ lithium chloride (LiCI) or lithium bromide (LiBr) as the desiccant liquid, and without significant impurities.
  • laboratory grade LiCI and LiBr may be utilized, with, e.g. , approximately 99.3% purity by weight (or the impurities will be less than 0.7%).
  • industrial grade LiCI and LiBr may be utilized, with, e.g., approximately 98% purity by weight (or less than 2% impurities).
  • Another factor to be considered for aqueous solutions is the purity of the water used in the desiccant solution.
  • RO water may be used instead of local tap water, because tap water may have impurities that crystallize out on heat exchanger and LAMEE surfaces, causing the performance of each to decrease until such time that these surfaces are cleaned with a solvent (e.g., mild acid).
  • a solvent e.g., mild acid
  • the desiccant liquid may be conveyed by pumps in a closed loop or loops between the LAMEE units and other components.
  • the semipermeable membrane material implemented in the LAMEE units may have homogeneously distributed micro-pores (e.g., 1 to 5 ⁇ ) of generally uniform sizes, with a relatively small standard deviation of diameter (e.g., less than 1 or 2 ⁇ ), and smooth internal surface structures (e.g. , surface roughness less than 100 nm), which helps to reduce the surface nucleation sites for the nucleation and growth of crystals.
  • micro-pores e.g., 1 to 5 ⁇
  • smooth internal surface structures e.g. , surface roughness less than 100 nm
  • examples of commercially available semipermeable membranes are QL822TM (General Electric, of Schenectady, NY, USA), and EZ2090TM (Celgard LLC, of Charlotte, NC, USA).
  • the LAMEE units' heat and moisture transfer membrane surface areas which transmit both heat and moisture to or from the air and solution flows through the semipermeable membranes, may each be selected or designed for the building application such that they will satisfy various system operating conditions, regardless of the weather and specified building conditions for air temperature and humidity, and while avoiding blockage of the membrane surface areas due to crystallization. Generally, this requirement may mean that the membrane surface areas of the exhaust LAMEE unit(s) plus the regeneration LAMEE unit(s) will be larger than that for the supply LAMEE unit(s).
  • the components used to control the systems described herein for summer supply air dehumidifying and cooling may differ from those used in winter for heating and humidifying air; i.e. the auxiliary loop 300 will not normally be used for winter operations.
  • the layout of the components in the systems may take several different forms, including, for example: (1 ) the components may be housed in a single HVAC unit, which is installed with electrical, water, natural gas and ducting connections, with the internal components sized for each particular application, and such a unit may be installed on roof tops or within a building envelope and used primarily for ventilation air conditioning with the exhaust and supply air discharge vents and supply air intakes in relatively close proximity; (2) a plurality of supply LAMEE units may be distributed throughout the conditioned space of a building, each with separate controls and connecting tubing to condition the internal building air to comfort conditions for the local occupants served by each unit, with separate fans to circulate the local air in situ for occupant comfort control; (3) a plurality of exhaust LAMEE units may be distributed on the building space exterior perimeter,
  • part or most of the outdoor ventilation air may be brought through the supply LAMEE unit, which will result in heating to form supply air to a set-point temperature and humidification level. This may necessitate the injection of water, e.g., by the water source 126 upstream of the supply LAMEE units 106a, 106b.
  • the saturation ratio S should be significantly less than 1 everywhere in this supply LAMEE unit (e.g., 1 >S).
  • crystallization avoidance within heat exchangers and semipermeable membrane exchangers for heat and moisture transfer for control of building occupant comfort and humidity conditions is a factor to be considered for HVAC system operations when salt solutions are used as the desiccant liquid.
  • Effective designs may use relatively high purity LiCI or LiBr salt solutions as coupling desiccant liquids, to avoid or reduce the risk of salt crystallization for a wide range of operating conditions.
  • Suitable semipermeable membranes may have good water vapor transfer and heat transfer resistance properties, good stress and strain and creep properties, and high liquid breakthrough transfer resistance, with relatively smooth internal pore surfaces and generally uniform micro-pore sizes to lessen crystallization nucleation.
  • Effective designs may also provide for larger heat and water vapor transfer surface areas for desiccant liquid cooling for regeneration/dewatering than for solution heating, air dehumidifying or processes with decreasing solution concentration.
  • Solution regeneration and dewatering may be done with the desiccant liquid at elevated temperatures (e.g., above 45 °C), and while the temperature of the solution is not decreasing due to a heat flux out of the solution. (The limiting temperature of the solution at which this regeneration or dewatering of the solution is carried out may be dictated by properties of the semipermeable membrane and the purity of the water used in the LAMEE units.)
  • the solution regeneration and dewatering may be done when the saturation state of the solution is not near 1 .0 [i.e.
  • (1 -S) does not approach 0].
  • the low temperature and high saturation condition required for the inlet of the supply LAMEE unit may be achieved by using a cooling only heat transfer process for the solution [i.e. so that (1 -S) may be moved by mostly cooling close to 0].
  • the systems described herein may also include features for improved energy savings that will lead to high values of COP, including, for example: economizer cycle with part load provisions for bypassing air; heat recovery for the desiccant liquid heating and cooling processes; waste heat recovery from any valuable heat source when it is economically feasible; heat recovery from the operation of dehumidifier mechanisms; moderate to low temperature change for the operation of the heat pump (allowing a high COP); and provisions for bypassing the desiccant liquid from the auxiliary loop during part cooling load conditions.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Central Air Conditioning (AREA)
  • Drying Of Gases (AREA)

Abstract

Système d'échange d'énergie pour conditionner l'air dans un espace intérieur d'une structure. Le système peut comprendre au moins une unité d'échangeur d'énergie à membrane liquide-air d'alimentation (LAMEE) pour conditionner l'air provenant de l'extérieur afin de former l'air d'alimentation pour l'espace intérieur, et au moins une unité LAMEE d'échappement pour collecter l'air depuis l'espace intérieur afin de former l'air d'échappement. Une boucle auxiliaire peut mettre en communication fluidique une sortie de liquide déshydratant de l'unité LAMEE d'échappement et une entrée de liquide déshydratant de l'unité LAMEE d'alimentation. Selon un premier mode, un liquide déshydratant est mis en circulation entre l'unité LAMEE d'alimentation et l'unité LAMEE d'échappement. Selon un deuxième mode, un liquide déshydratant est mis en circulation entre l'unité LAMEE d'alimentation, l'unité LAMEE d'échappement et la boucle auxiliaire, et une teneur en eau du liquide déshydratant est réduite dans la boucle auxiliaire.
PCT/CA2015/051161 2014-11-10 2015-11-10 Systèmes et procédés d'échange d'énergie WO2016074077A1 (fr)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107575959A (zh) * 2017-09-20 2018-01-12 中国科学院上海高等研究院 空气热湿处理系统
WO2018191805A1 (fr) * 2017-04-18 2018-10-25 Nortek Air Solutions Canada, Inc. Systèmes et procédés de gestion de conditions dans un espace renfermé
WO2023092213A1 (fr) * 2021-11-24 2023-06-01 Nortek Air Solutions Canada, Inc. Échangeur de chaleur parallèle pour refroidissement de centre de calcul
US11892193B2 (en) 2017-04-18 2024-02-06 Nortek Air Solutions Canada, Inc. Desiccant enhanced evaporative cooling systems and methods

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006006177A1 (fr) * 2004-07-14 2006-01-19 Agam Energy System Ltd. Systemes et procedes pour deshumidification
WO2011161547A2 (fr) * 2010-06-24 2011-12-29 Venmar, Ces Inc. Echangeur d'énergie à membrane liquide/air
WO2012071036A1 (fr) * 2010-11-23 2012-05-31 Ducool Ltd. Système de conditionnement d'air
WO2013029148A1 (fr) * 2011-09-02 2013-03-07 Venmar Ces, Inc. Système d'échange d'énergie pour conditionnement de l'air dans une structure fermée
CA2901483A1 (fr) * 2013-03-15 2014-09-18 Nortek Air Solutions Canada, Inc. Systeme et procede de commande pour un systeme de distribution d'air a deshydratant liquide

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006006177A1 (fr) * 2004-07-14 2006-01-19 Agam Energy System Ltd. Systemes et procedes pour deshumidification
WO2011161547A2 (fr) * 2010-06-24 2011-12-29 Venmar, Ces Inc. Echangeur d'énergie à membrane liquide/air
WO2012071036A1 (fr) * 2010-11-23 2012-05-31 Ducool Ltd. Système de conditionnement d'air
WO2013029148A1 (fr) * 2011-09-02 2013-03-07 Venmar Ces, Inc. Système d'échange d'énergie pour conditionnement de l'air dans une structure fermée
CA2901483A1 (fr) * 2013-03-15 2014-09-18 Nortek Air Solutions Canada, Inc. Systeme et procede de commande pour un systeme de distribution d'air a deshydratant liquide

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018191805A1 (fr) * 2017-04-18 2018-10-25 Nortek Air Solutions Canada, Inc. Systèmes et procédés de gestion de conditions dans un espace renfermé
CN110809698A (zh) * 2017-04-18 2020-02-18 北狄空气应对加拿大公司 用于管理封闭空间中的条件的系统和方法
US11892193B2 (en) 2017-04-18 2024-02-06 Nortek Air Solutions Canada, Inc. Desiccant enhanced evaporative cooling systems and methods
CN107575959A (zh) * 2017-09-20 2018-01-12 中国科学院上海高等研究院 空气热湿处理系统
WO2023092213A1 (fr) * 2021-11-24 2023-06-01 Nortek Air Solutions Canada, Inc. Échangeur de chaleur parallèle pour refroidissement de centre de calcul

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