A new concept of HRV---Bidirectional flow heat-exchanger Fan

aaa-1234

high effective, energy saving, easy maintenance, low cost

Inscription: the design achieved small sized ( length 1m, diameter 0.5m) relatively simple structure, appr. 40W power consumption, 150m3/h flow rate, 76.8% --86.4% temperature exchange efficiency, winter Energy Efficiency Ratio close to 30.  No need to change components and no consumptive materials during whole life cycle, easy to clean and maintain. All of the above is impossible for any of the current on sale HRV (Heat Recovery Ventilator).


Background
The current on sale HRV (Heat Recovery Ventilator) is an air ventilation apparatus with heat recycling function.  It improved the room air quality, meanwhile reduced the influence to the room temperature as much as possible. For example, current Lossnay heat-exchanger (static heat exchanger) consists of a shell, two blower fans and a heat-exchanging module. The heat-exchanging module is made of paper, the stacking of the paper plate form the perpendicular air channels. This structure can separate the absorbed air and the expelled air in their respective air channels, conduct the sensible heat exchange (heat conduction) and latent heat exchange (condensation- capillarity-evaporation ) and draw the fresh air into indoor environment.   
But it has some main disadvantages as below:
1、Need 2 blower fans for air input and output;
2、High thermal resistance and flow resistance, which cause low heat exchange and high power consumption;
3、Paper material need to be changed often;
4、Condensation water may frost, caused low actual sensible heat and latent heat exchange efficiency；

                               
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New solution
It is therefore the inventor of the present invention provided the revolutionary new solution after long time research and improvement.

                               
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The characteristic is: the new HRV comprises a gyrator heat-exchanger assembly, a shell, the first and second end; the gyrator heat exchanger assembly consists of inner cylinder, outer cylinder, and the hollow axial flow vanes between the inner and outer cylinders.（the blue arrows in above figure represent for entrance of cold outside air）  
The advantages are:
1、A large number of hollow axial flow vanes with heat exchange function compose the gyrator heat-exchanger assembly. Instead of 2 blower fans and 1 static heat-exchanger module in the original technology, its 3-in-1 structure significantly simplified the apparatus, and changed the flow resistance in the original technology into the motive force in the new invention.
2、The vanes are made of metal material, which not only reduces the thermal resistance, the “blade” type heat exchanger also enhances the heat conductivity, and prolong the life of the heat-exchanger.   
3、The condensation water transfer during latent heat exchange process is done by centrifugal force, comparing the original technology of capillarity, it realized thorough condensation water transfer, promoted the condensation-evaporation process, and then enhanced the latent heat exchange efficiency.  
4、The rotating metal heat exchanger is easy to clean, so that the sanitation standard is enhanced.
The disadvantage is: there might be little air leakage due to the non-contact axis seals.

                               
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Remark: 3In1 -- The hollow vanes play more than 3 roles:
1)        Heat exchanger: hot air is outside of the hollow vanes, while cold air is inside.
2)        Axial fan: The shape of hollow vanes in rows is just the same as an axial flow fan.
3)        Centrifugal fan: When rotating the hollow vanes drive the inside air flow towards centrifugal direction;
Moreover, it also functions as a centrifugal pump to fling out the condensation water.  

We performed computer simulation on the new HRV. After multiple optimization, we finalized the vanes parameters and achieved air-volume balance (equal air flow on both ends).
The computer simulation is based on the summer and winter senarios. The temperature distribution in the cold and hot air channels is calculated by adopting the CFD data simulation method. The calculation error of exchanging efficiency is within 5%. 7760 thousands grids in hot air channel area, 4570 thousand grids in cold air channel area, total 12330 thousand grids. In combination with energy equation solver, K-epsilon turbulent model adopting renormalization-group theory, multiphase flow model, phase transformation compositional model (condensation of super-saturated air), the calculation result has high reliability.  

                               
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Summer conditions（no condensation water）（outdoor temp.33°C / humidity 63%, indoor temp. 26°C / humidity 50%，power consumption 37W）：
Cold air temperature(K)：299à305.7
Cold air flow rate：0.042 kg/s
Cold air heat flux:  269.8 w
Hot air temperature(K)：306à300.6
Hot air heat flux：269.8 w
Hot air flow rate：0.048 kg/s
Flow ratio（cold air flow rate/ hot air flow rate x 100%）: 87.5%
Total heat exchanged：269.8 W
Power consumption：37.4W
Average temperature exchange rate (absolute value of average temp. rise / temp. diff. indoor and outdoor x 100%) : 86.4%
Energy efficiency ratio (recycled heat/input electricity power): 7.21

                               
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Winter conditions Northern city（Outdoor -10°C / humidity 30%, indoor temp. 20°C / humidity 50%, power consumption 41W）:
Cold air temperature(K)：263à285.6
Cold air flow rate: 0.054 kg/s
Cold air heat flux： 1236.9 w
Hot air temperature(K)：293à269.5
Hot air heat flux：1236.9 w
Hot air flow rate：0.052 kg/s
Flow ratio（cold air flow rate/ hot air flow rate x 100%）：103.8%
Total heat exchanged： 1236.9 W
Power consumption：41.1W
Average temperature exchange rate (absolute value of average temp. rise / temp. diff. indoor and outdoor x 100%)：76.8 %
Energy efficiency ratio (recycled heat/input electricity power)：29.9

                               
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Winter conditions Southern city (（Outdoor  0°C / humidity 50%, indoor temp. 20°C / humidity 50%, power consumption 40W）
Cold air temperature(K)：273à288.3
Cold air flow rate：0.053 kg/s
Cold air heat flux： 817.6w
Hot air temperature(K)：293à277.1
Hot air heat flux：817.6 w
Hot air flow rate：0.051 kg/s
Flow ratio（cold air flow rate/ hot air flow rate x 100%）：100%
Total heat exchanged：817.6 w
Power consumption：40.3 w
Average temperature exchange rate (absolute value of average temp. rise / temp. diff. indoor and outdoor x 100%)：78%
Energy efficiency ratio (recycled heat/input electricity power)：20.2

http://www.cfluid.com/bbs/attachment.php?aid=25959&k=aa987fb84d2475ea3cd2784dfee4806d&t=1392686169&noupdate=yes
http://www.cfluid.com/bbs/attachment.php?aid=25960&k=bb801e1ad878ae1f87b950f5f7df371c&t=1392686169&noupdate=yes

In summer, the viscosity and density of air is lower, so the heat exchanging is more sufficient, the temperature exchange rate is a little higher than in winter; whereas in winter, the temperature difference is bigger, so energy efficiency ratio is higher than in summer.
Normal heat exchangers generate condensation water covering on the structure surface (even form a frost layer), which therefore reduce the heat conductivity and the heat exchange efficiency. The condensation water is concentrated at the area shown in below figure.
After improved in this invention, the air channels become simpler, the condensation water as illustrated below, is easily to be flung out of hot air channel by centrifugal force (600 rpm rotating), through the perforations in the outer cylinder, to the adjoining cold air channels and evaporates. Thus the heat exchange efficiency will not be reduced due to the condensation water.
All of the previous inventions are not able to eliminate condensation water.
The figure below shows the condensation water distribution.

                               
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[ 本帖最后由 aaa-1234 于 2014-2-18 09:25 编辑 ]

aaa-1234

similar to Southern winter cold working condition of China

                               
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This is the LEER designed standard working condition, the flow ratio of cold and hot air is 1:1, it is applicable to most of areas in China.
Explanation on Table 1 and Chart 1:  
P1,P2,P3 --- hot air parameter points;  P1,P2,P3,P4,P5 --- cold are parameter points; T- dry-bulb temperature; RH – relative humidity, AH – absolute humidity;  E – enthalpy;  HV – hollow vane


1)        Hot air channel
P1 is the entrance, hot air come from indoor flow outside the hollow vane.
During P1-P2 process the dry-bulb temperature T gradually decreases, the relative humidity RH gradually increases. Because the hollow vane are made of metal material, there is no water exchanging, the absolute humidity AH remains no change. When reach P2, the RH get 100%, condensation water starts. P1-P2 line segment is the isohume, point P2is at the intersection of the isohume and saturated humidity line.
During P2-P3 process T keep dropping, RH remains 100%, the increasingly generated condensation water transferred to the cold air channel through the perforations on the cylinder under centrifugal, P2-P3 line segment is coincided with the saturated humidity line.  
When reaching exit P3, T decreased to 4.1 0C, RH still remains no change, the AH reached lowest (5.06). In the above process, the enthalpy exchanged 21.8kj/kg, in which latent heat exchange takes 25%.


2)        Cold air channel
P1 is cold air entrance, the cold air come from outside, the flow inside the hollow vane.
P1 – P2, the cold air get through the first groups of hollow vane, there is only sensible heat exchange, no humidity exchange. When reaching P2, T=5, RH=35, AH=1.88. As AH didn't change, therefore P1-P2 is the AH isohume.
P2-P3 is the isoenthalpy line, the exit of group 1 HV and the entrance of group 2 HV is a “long and narrow channel”, the heat exchanging area is very small and can be considered as an adiabatic process.  The condensation water transferred from hot air channel evaporates here until reached dew point.  
P3 is at the intersection of this isoenthalpy line and the saturated humidity line. Line segment P3-P4 is coincided with the saturated humidity line.
P4 is at the inside of group 2 hollow vane (HV), as the condensation water didn’t evaporated completely in the “long and narrow channel”, the leftovers will evaporate inside the group 2 hollow vane( HV), and totally evaporate along with the increment of T and AH. This point is P4, at the intersection of the saturated humidity line and next isohume(P4-P5).
P4-P5 is isohume. When the air flowing to exit, T is keep increasing and RH keep decreasing, E is also increasing gradually, until exit P5, T=15.3, RH=37.9, D=4.06, E=25.7.
During P4-P5 the whole heat exchange process, E increased 21kj/kg, in which latent heat exchange takes 26%.

[ 本帖最后由 aaa-1234 于 2014-2-18 09:36 编辑 ]

aaa-1234

                               
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The principle of this condition is similar to am. 1 average working condition, but there appears frost phenomenon which makes it more complicated. Under frost phenomenon the air parameters in table 2 and chart 2 are not realizable, and can only for analysis reference. The control point of frosting is P3(red and blue), because it is estimated that frosting could be avoided when outside temperature is higher than -3 0C, so when it is needed to operate under -3 0C, below measures should be taken: 1) add air preheat device; it is not wasting heat energy as in cold weather it is necessary to enhance heat supply load anyway.   2) intermittently operating LEER, and add melt water removal device.

aaa-1234

                               
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According to Table 3 and Chart 3, there is no condensation water generated in summer average condition, no latent heat exchange, therefore the entrance and exit of LEER are the same as in winter; but in case of high humid weather, there might be condensation water coming into inside rooms, this is not what we want. Is it possible to switch the entrance and exit of LEER when season changes.

aaa-1234

                               
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According to Table 4 and Chart 4, different from 1 and 2, look at the blue line, P3 is not at the saturated humidity line. When RH reaches 78.5%, the condensation water evaporated completely, the isoenthalpy evaporation process of P2-P3 caused the temperature decreased to about 220C. The relatively bigger temperature difference can increase the heat exchange amount. And more exhilarating, in high humid weather, the heat exchange result is very good and the sensible and latent heat exchange rate is 1:1. It is worth doing to switch the entrance and exit when season changes even it brings a little trouble.