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predicting the performance of an active magnetic regenerator refrigerator used for space cooling and refrigeration.

by:Maghard      2020-02-25
Active magnetic regeneration refrigeration (AMRR)
The system represents an environmental attractive refrigeration alternative that does not use the work of carbon-fluorine compounds.
Recently, the alloy series of magnetic materials with adjustable temperature in the Curie point has been developed.
Using these materials, a layered regeneration bed can be constructed to achieve high magnetic thermal effects throughout the operating temperature range.
This paper describes a numerical model that can predict the actual performance limits of this technique applied to space.
Air conditioning and refrigeration applications.
The model regards the regeneration bed as-
The size matrix of the magnetic material, which has a spatial change in the temperature of the Curie point, is therefore magnetic.
The matrix is affected by the magnetic field and fluid mass flow rate of spatial and temporal changes.
The numerical model is solved using a fully implicit discrete control energy equation.
Nonlinear aspects of governing equations (e. g.
, Fluid and magnetic changes)
Operate with relaxation technology.
The modeling results illustrate how to optimize the AMRR system for specific operating conditions.
Performance of layered and non-layered AMRRs compared with current space steam compression techniques
Adjustment and refrigeration applications.
Introduce a well
The designed magnetic cooling system may compete with the space steam compression system
Cooling and refrigeration applications.
There is basically no evaporation pressure for metal refrigerants, no ozone consumption potential or direct global warming potential.
Active magnetic regeneration refrigeration (AMRR)
The system may also have advantages over noise, control, and componentsloadefficiency.
Zimm and others developed and demonstrated the structure of the rotating bed. (2002);
It achieves a medium level of COP and can use affordable permanent materials.
At the same time, the development of magnetic materials with \"adjustable\" dwell point temperature allows the manufacture of layered magnetic regeneration beds that exhibit large magnetic thermal effects over a large temperature range (
Smaili and Chahine1997).
Steam compression is a mature technology.
Fundamental performance limits due to inherent throttling, compression, and heat exchange processes.
Irreversible throttling and compression losses are avoided in the magnetic system, although new heat dissipation mechanisms such as pumping losses through the bed layer and additional heat transfer losses in the recycler are encountered. Awell-
The designed magnetic system may compete with the steam compression system, even more efficient than the steam compression system.
This paper uses physics-
The actual limit of the efficiency of the magnetic cooling cycle is predicted based on the numerical model, and the AMRR cycle is compared with the current technology.
The thermal and magnetic properties of magnetic thermal materials are highly coupled in a specific, usually very small temperature range, allowing them to be used in an energy conversion system. Temperature(T)and entropy (S)
A common property pair of a specification is formed, and together they define the transfer of heat.
If the lag is ignored, the field is applied ([[mu]. sub. o]H)
Magnetic moment (VM)
Describe the transfer of magnetic work (Guggenheim 1967).
The fundamental properties relationship of substances capable of experiencing magnetic work is given in equation 1. dU = TdS + [[mu]. sub. o]
That is, when there is a change in the magnetic field, this simplification reduces the performance of the recycler.
Approximate techniques for correcting this assumption are discussed later.
After removing the heat capacity of the trapped fluid, the axial conduction term is moved to the regeneration equation and the pressure gradient is represented by the friction factor, and equation 2 becomes [dot. m][c. sub. f][[[
Partial derivative[T. sub. f]]/[
Partial derivative]x]+ [[Nu[k. sub. f]]/[d. sub. h]][a. sub. s][A. sub. c]([T. sub. f]-[T. sub. r]= |[f[dot. m. sup. 3]]/[2[[rho]. sub. f. sup. 2][A. sub. c. sup. 2][d. sub. h]]|. (3)
The energy balance of the magnetic material in the recycler is [[Nu[k. sub. f]]/[d. sub. h]][a. sub. s][A. sub. c]([T. sub. f]-[T. sub. r]+[A. sub. c])(1 -[epsilon])[[mu]. sub. o]H[[
Partial derivative]M/[
Partial derivativet]+ [k. sub. eff][A. sub. c][[[[
Partial derivative]. sup. 2][T. sub. r]]/[[
Partial derivative[x. sup. 2]]]=[[rho]. sub. r][A. sub. c](1 -[epsilon])[[[
Partial derivative][u. sub. r]]/[
Partial derivativet], (4)
The first term represents the heat transfer from the fluid to the generator, the second term represents the magnetic work transfer, the third term is through the effective axial conduction of the recycler and the fluid, and the fourth term is energy storage.
The magnetic work term is grouped with changes in the internal energy of the matrix in order to obtain an expression that involves the entropy partial derivative of the magnetic field at a constant temperature.
The thermal capacity of the fluid removed from Equation 2 is added to the energy balance of the generator, so that the control equation of the generator becomes. [[Nu[k. sub. f]]/[d. sub. h]][a. sub. s][A. sub. c]([T. sub. f]-[T. sub. r])+ [k. sub. eff][A. sub. c][[[[
Partial derivative. sup. 2][T. sub. r]]/[[
Partial derivative][x. sup. 2]]]= [A. sub. c](1 -[epsilon])[[rho]. sub. r][T. sub. r][[[
Partial derivative][s. sub. r]]/[[
Partial derivative[[mu]. sub. o]H]]|[[[
Partial derivative][[mu]. sub. o]H]/[
Partial derivativet]+[A. sub. c][[[rho]. sub. f][epsilon][c. sub. f]+(1 -[epsilon])[[rho]. sub. r][c. sub. [mu]. sub. o]H][[[
Partial derivative][T. sub. r]]/[
Partial derivativet]. (5)
The boundary conditions of Equation 3 and equation 5 require the fluid to enter the matrix at the temperature of the associated thermal reservoir.
Assuming that the end of the recycler is insulated from the conductive heat transfer, the recycler must go through a stable-state cycle.
The last boundary condition results in a constraint that the temperature at any position in the generator is consistent with the temperature at the same point in time t [tau], where [tau]
Duration of the cycle.
These boundary conditions are summarized in Table 1.
The numerical model extends from 0 to L in space, and extends from 0 to the numerical solution of the temperature of the fluid and the recycler obtained on the grid [tau]in time.
The initial \"guess\" value of the temperature of each node ([T*. sub. ri,j]and [T*. sub. fi,j])
Based on local linear and time allocation
Assumption unchanged.
Properties, local flow properties and other temperatures-
Based on these \"guessing\" temperature values, the relevant aspects of the matrix properties are calculated for each control volume.
The analytical matrix decomposition algorithm is used to linear, discrete and solve the fluid and regenerative control equations.
The absolute value of the maximum error between the \"guess\" value of the generator and the fluid temperature and the calculated value is determined--
If the error is less than the specified relaxation tolerance 5.
0 mK, the release process is completed;
Otherwise, use a new set of \"guess\" values in subsequent iterations.
These new \"guess\" values ([T*. sup. (+)])
Calculated as a weighted average of the calculated value and the \"guess\" value.
Numerical model of Additionaldetails Engel Brecht (2005).
Material properties specific heat, thermal conductivity and viscosity of water and other heat transfer fluids, such as propylene alcohol and ethylene glycol solutions, are expressed as functions of temperature with polynomial associations.
The experimental performance data of 94% gd/6% er alloy * was used by using two-
Dimension Flower line technology.
The interpolation entropy data is distinguished by numerical values to determine the required model input: the constant field specific heat capacity and the partial derivative of entropy relative to the application field.
Although the model is generally applicable to many matrix structures, the initial analysis focuses on the packaged sphere generator.
The total axial conductivity of the regeneration bed is the sum of the dispersed conductivity ,[k. sub. f][D. sub. d]
And the static effective thermal conductivity ,[k. sub. static], where [D. sub. d]
It is the dispersion coefficient of boundless. [k. sub. eff]= [k. sub. static]+ [k. sub. f][D. sub. d](6)
Introduction to the calculation of Hadley packedsphere of electrostatic guide fluid/regenerative matrix by linear method (1986). [k. sub. static]= [k. sub. f][(1 -[[alpha]. sub. 0])[[[epsilon][f. sub. 0]+ [k. sub. r]/[k. sub. f](1 -[epsilon][f. sub. 0])]/[1 -[epsilon](1 -[f. sub. 0])+[k. sub. r]/[k. sub. f][epsilon](1 -[f. sub. 0])]]+[[alpha]. sub. 0][[2([k. sub. r]/[k. sub. f])[. sup. 2](1 -[epsilon])+(1+2[epsilon])[k. sub. r]/[k. sub. f]]/[(2 + [epsilon])[k. sub. r]/[k. sub. f]+1 -[epsilon]]]]. (7)[f. sub. 0]= 0. 8 + 0. 1[epsilon](8)log[[alpha]. sub. 0]= -4. 898[epsilon]0 [
Less than or equal to][epsilon][
Less than or equal to]0. 0827. log[[alpha]. sub. 0]= -0. 405 -3. 154([epsilon]-0. 0827)0. 0827 [
Less than or equal to][epsilon][
Less than or equal to]0. 298 log[[alpha]. sub. 0]= -1. 084 -6. 778([epsilon]-0. 298)0. 298 [
Less than or equal to][epsilon][
Less than or equal to]0. 580 (9)
Related introduction to the calculation of axial distribution byKaviany (1995). [D. sub. d]= [epsilon][3/4]P[e. sub. f], P[e. sub. f][
Much better than this. 1 (10)where P[e. sub. f]
Peclet number of flow defined as asP [e. sub. f]= R[e. sub. f]P[r. sub. f].
Calculate the friction coefficient with the Ergun equation of the constant suggested by Kaviany (1995). [f. sub. f]= 360[[(1 -[epsilon])[. sup. 2]]/[[[epsilon]. sup. 3]xR[e. sub. f]]]+ 3. 6[1 -[epsilon]/[[epsilon]. sup. 3]](11)
The number of Nusselt is calculated using the correlation of the filler bed ball given by wakaao and Kaguei (1982). N[u. sub. f]= [2[epsilon]/3(1 -[epsilon])](2. 0 +1. 1R[e. sub. f. sup. 0. 6]P[r. sub. f. sup. 1/3])(12)
The internal temperature gradient of the design of the actual filling ball generator, the number of Biot (Bi)
Throughout the cycle, especially during the flow, the unity associated with magnetic materials is generally not much less.
Therefore, it cannot be considered that the temperature inside the sphere that constitutes the matrix is uniform in space.
As a result, the heat transfer from the fluid to the magnetic material is significantly affected by the conduction from the center of the sphere to the outer surface and the convection from the surface of the sphere to the fluid.
By calculating the modified heat transfer coefficient ([h. sub. eff])
As jeffreson suggested (1972)
According to equation 13. [h. sub. eff]= h/[1+[Bi/5]](13)
In most applications using recycled heat exchangers, the thermal capacity of the fluid is small relative to the thermal capacity associated with the substrate itself of the recycler.
However, the AMRR system used in space
Liquid heat transfer liquid for cooling application;
Therefore, the thermal capacity of the fluid contained in the matrix is significant.
In the actual AMRR design, the capacity of the carried fluid may be equal to the thermal capacity of the substrate.
Therefore, when the AMRRsystem is simulated with a liquid heat transfer fluid, the thermal capacity of the trapped fluid cannot be ignored.
Neris and Klein (2006)
A method has been developed that can be used to approximate correction of the capacitance assumptions presented during the development of the Numerical heat exchanger model-
That is to say, the thermal capacity of the fluid and the generator is combined in the control equation.
The method was developed for passive reheater and a correction factor applied to the heat transfer coefficient was provided;
Heat transfer enhancement coefficient ,[h. sub. aug], is given by [h. sub. aug]= [h. sub. eff](1 + 1. 7640R + 1. 0064[R. sup. 2]), (14)
Where R is the ratio of the fluid thermal capacity as defined in Equation 15 to the heat capacity of the recycler. R = [[[rho]. sub. f][c. sub. f][epsilon]]/[[[rho]. sub. r][c. sub. r](1 -[epsilon])](15)
The basic output of the model output model is the refrigeration capacity ([dot. Q. sub. refrigeration])
Heat dissipation ([dot. Q. sub. refection])
Magnetic work into the regeneration device ([dot. W. sub. mag])
Here at sticicsteady-Status operation.
The heat discharge and cooling load are recalculated by numerical integration :[dot. Q. sub. rejection]=-[1/[tau]][[tau]. [integral]. 0][dot. m][h. sub.
Therefore, as indicated by the proximity temperature difference, the performance does not remain the same as the mass flow rate of the heating agent (
Heat transfer fluid in this case)is varied.
Therefore, an iterative calculation is required to ensure the reservoir temperature used as the boundary condition for fluid temperature of the active magnetic regeneration bed numerical model ([T. sub. H]and [T. sub. C])
Consistent with the mass flow rate and operating temperature of the air and heat transfer fluid.
The analysis of the cold heat exchanger must take into account the large amount of condensation occurring on the cold heat exchanger.
Heat transfer and dehumidifying of cold heat exchangers are modeled using a heat transfer analogy similar [epsilon]-
University of Taiwan, such. (1989).
There is no potential enthalpy change in the heat transfer fluid, as in the vapor compression cycle with the refrigerant, due to the magnetic induced effect, the temperature change in the heat transfer fluid is relatively low;
Therefore, the mass flow rate of heat transfer in the AMRR system will be significantly higher than the refrigerant flow rate in the comparable steam compression system.
Therefore, care must be taken in the design of the heat exchanger to avoid high impact losses associated with the flow through the heat exchanger.
It may also be necessary to increase the diameter of the connecting pipe to avoid high pumping loss.
In this analysis, the pressure drop and fan power on the air side are considered and included in the system COP on the air side
Adjustment application.
However, the additional pressure drop associated with the flow of the liquid through the hot and cold heat exchanger is ignored, as it has been shown that there is a good design, relative to the pressure drop through the AMRR bed itself, it can become small.
The phenomenon of being ignored the factor for the thermal capacity correction proposed in the previous section is developed for passive heat return.
It is not fully understood how the heat capacity of the Cobble affects the performance of the active magnetic recycler, although the correction factor of the active recycler is currently being studied.
Regardless of the additional pumping power associated with the acceleration and deceleration of the fluid in the recycler.
For operations with relatively low frequency (e. g.
, Operating nearly 5Hz)
The influence of fluid oscillation is small;
However, in order to allow for smaller equipment, more advanced cycles may operate at higher frequencies, thus taking advantage of the more favorable economic benefits associated with these design points.
Therefore, for more advanced cycles running at higher frequencies, the heat transfer, dispersion, and pressure drop associations currently used in the model may be inaccurate.
The study of the influence of oscillating flow on the performance of passive regeneration devices found that the heat transfer increased and the pressure drop increased relative to stable flow (
Zhao Mou and Cheng MOU [1996]).
The effect of the primary flow can be explained by an appropriate Association, which is a function of the Strouhal number or the number of Valencia and the number of Renault and the number of planters.
Correction of the internal temperature gradient used in the model, which has been discussed before, assuming stability-
Conduction through the state of the solid material.
At high frequencies, the thermal penetration depth associated with cycle time may become unmatched within the spatial range of the local matrix structure, indicating that the entire matrix is not involved in the heating process.
This effect can be explained by a correction factor, which is a function of the Fourier number and the Biot number.
Results The technical results of selecting aspect ratio and mass flow rate are given in the subsequent sections of the refrigeration and spatial regulation applications under specific operating conditions including cold loads.
The technical maturity of the AMRR technology limits the internal geometry, material and working frequency of the active magnetic regeneration bed and specifies the conditions for these studies.
The remaining free parameters are the volume and aspect ratio of the Recycler (
Defined as the ratio of length to length-sectional area)
And heat transfer fluid flow rate.
Figure 2 illustrates the behavior of the refrigeration capacity and performance coefficient, COP (
Defined as the ratio of the heating capacity to the sum of the power of the motor, pump and fan)
, The asa function of the fluid mass flow rate of a typical AMRR system.
Note that in the case of a very low mass flow rate, the regenerator acts as a hot short joint between the hot and cold reservoirs, so both the heat release capability and the COP are negative.
With the increase of mass flow, the system is able to produce refrigeration proportional to mass flow, so both refrigeration capacity and COP are increased.
At some point, the loss caused by fluid flow overpowered the conductive loss, and the COP reached the maximum value, which occurred at a very low mass flow rate and then decreased.
In the end, the mass flow rate becomes large enough to exceed the magnetic thermal effect shown by the bed layer, after which the heating capacity is reduced.
At extremely high mass flow rate, when the fluid entering the cold storage is higher than the cold storage temperature, both the refrigeration capacity and the COP become negative. [
Figure 2:
Note that a horizontal line may be drawn in figure 2, corresponding to the specific required cooling capacity.
Unless the specified refrigeration capacity exceeds the maximum capacity of the system, the horizontal line will intersect the capacity curve at two points, each corresponding to a different mass flow rate;
The lower mass flow corresponds to the higher COP, so it is always the right choice.
Therefore, select the lower mass flow rate operating point corresponding to the specified refrigeration load for all subsequent results.
The regeneration bed also has an optimal aspect ratio.
Figure 3 illustrates the general behavior of COP as a function of the volume aspect ratio of a given recycler;
Note that in order to produce this curve, it is necessary to select the mass flow rate in each value of the aspect ratio in order to obtain the required cooling capacity using the process described earlier.
Figure 3 shows the best aspect ratio of the COP that exists to maximize the bed;
Low aspect ratio leads to pancakes
The forming bed with excessive conduction loss, while the higher aspect ratio leads to excessive pumping loss.
In the following results, in the context of specific applications and AMRRconfiguration, the optimal mass flow rate and aspect ratio are selected as a function of the volume of the recycler. [
Figure 3 slightly]Space-
The predictive performance of the cooling application AMRR system is compared with the astandard steam compression system
Cooling application.
Default conditions for DOE/ORNL heat pump design model (Rice 2005)
Used to represent a steam compression system.
Table 2 summarizes the parameters used for comparison.
The active magnetic return heat body bed model coupled to the previously described heat exchanger model is operated to determine how the system performance changes with the volume of the heat return, in terms of optimal ratio and mass
For the conditions summarized in Table 2, the DOE/ORNL heat pump design model predicted COP 3.
The baseline steam compression period is 10, including 0.
59 KW of fan power.
The AMRR system model then runs under the same conditions and uses the same heat exchanger size (
As shown in UA value in table 2)
And air flow.
The numerical model does not explicitly model the fan power associated with the airflow rate;
Therefore, the fan power predicted by the heat pump design model is added to the total power predicted by the numerical model to calculate the system COP of the AMRR cycle.
Note that the presented COP corresponds to the ratio of the temperature provided to the sum of the power of the motor, pump and fan.
Figure 4 illustrates that the predicted COP is a function of the regeneration volume of a layered and non-layered bed;
These curves are generated for the cooling capacity of 8.
76 KW and the optimum aspect ratio and flow rate for each value of the regenerator volume.
The layered recycler is modeled to have a Curie temperature that linearly changes along the bed from the AMRR heat reservoir temperature to the old reservoir temperature, rather than a layered recycler contains materials with a constant Curie temperature which is the average value set at the temperature of the hot and cold reservoir.
As mentioned earlier, the properties of magnetic materials represent 94% gd/6% er alloys.
Figure 4 shows that the AMRR cycle may have a higher COP value than the equivalent vapor compression cycle;
However, the COP that can be achieved using AMRR is strongly dependent on the volume of the magnetic regeneration bed
The layered bed may be much smaller than the non-layered bed.
Note that the volume shown in figure 4 corresponds to the total volume of all six recyclers beds, but does not include any allowance for external hardware (e. g.
Heat net, heat exchanger shell, motor, pump, heat exchanger, etc. ).
With the increase of generator volume, the operation efficiency is improved. [
Figure 4 slightly]
The sensitivity of the COP of the AMRR system to thermal inhibition temperature was studied by using the joint regeneration device design (
Volume and aspect ratio)
A bed on one floor.
Selected recycler designs were selected so that the COP predicted under design conditions was higher than the equivalent steam compression system, and the COP of the layered and non-layered recyclers was roughly equal;
These options are shown in figure 4, as shown in design (
3 L layered bed with 1.
The mass flow and aspect ratio of 20 kg/s are 0. 15)and B (
10l non layered bed with a1.
The mass flow and aspect ratio of 43 kg/s are 0. 15).
The regeneration bed layer material, therefore, the temperature distribution of the Curie point in the regeneration bed layer remains unchanged at the value used for development Figure 4.
Heat discharge temperature (
Air temperature entering the heat exchanger)
Changes when the cooling capacity remains the same.
76 KW by changing the mass flow rate of the fluid as needed.
Design the COPs of A and B as shown in figure 5 as A function of the temperature of the heat reservoir (i. e.
Temperature of ambient air).
In figure 5, the layered bed is no longer able to produce 8.
76 KW, regardless of the mass flow rate, when the heat discharge temperature exceeds about 320 K (116[degrees]F)
, When the heat suppression temperature is higher than 325 K, the required cooling cannot be generated by a non-layered bed (135[degrees]F).
As the thermal insulation temperature increases from the design temperature of 30, the performance coefficient of the non-layered bed is slightly higher than that of the layered bed. 2 K (95. 1[degrees]F). This non-
The intuitive result is that the material in the layered bed is specially selected to maximize the magnetic thermal effect over a specific temperature range.
Because the maximum change of entropy relative to the magnetic field occurs in an arrow temperature range of the material studied here, when the temperature range changes, the magnetic thermal effect of the layered bed is reduced relatively high.
The non-layered bed is composed of a material whose dwell point temperature is selected as the mean of the temperature of the hot and cold reservoir.
With the increase of the heat reservoir temperature, the magnetic thermal effect is reduced, but the maximum magnetic thermal effect can still be achieved at a certain position in the bed layer, and the performance of the non-layered bed is lower than the performance of the layered bed. [
Figure 5 Slightly]
It is important to quantify the main loss of the well
Design the system.
This information can be used to evaluate risk areas in modeling, to guide additional research, and to provide insights into the design of advanced recyclers.
Performance losses associated with each entropy generation mechanism have been quantified separately by the specific loss mechanism in the \"off\" model while keeping all other loss mechanisms unchanged.
Changes in system performance are caused by the deactivation of specific loss mechanisms, which provides a measure of its importance.
This analysis assumes that the main mechanism of loss does not interact.
Since each loss mechanism is deactivated, the fluid mass flow rate is adjusted to provide the same cooling power.
The change of input power indicates the corresponding performance improvement.
The main loss mechanism used in the AMRR system for space conditions is pumping loss, loss caused by viscosity dissipation, axial Conduction caused by dispersion, axial Conduction caused by static conduction through the bed layer of the recyclerSolid and fluid)
, Temperature difference of heat transfer in heat exchanger and cold exchanger, motor loss and heat exchanger loss.
The nominal AMRRdesign point used for parameter studies is the design case a in figure 4, which corresponds to a 3 L layered bed with an aspect ratio of 0. 15.
Figure 6 summarizes the results of this study.
The non-refrigeration COP of the cooler operating at the temperature of the hot and cold reservoir specified in Table 1 is 35.
7, corresponding to the work input of 0.
25 KW, and under these conditions, the predicted workload of design A is 2. 31 kW.
The difference between these values, 2.
06 KW, so it can be attributed to the various losses listed earlier.
The relative contribution of these indicators is shown in figure 6. [
Figure 6 slightly]
Figure 6 shows that the main loss directly controlled by the magnetic recycler bed is related to the pumping loss due to the falling of the top of the recycler, the conduction and imperfect heat transfer inside the recycler;
These are approximately equal, which is the result of the design process described earlier, which is used to specify design point.
On the outside of the heat return bed, the heat exchange and fan loss associated with the hot and cold heat exchanger are large;
These losses are also important in the evaporation compression cycle.
The importance of the internal recycler loss shown in Figure 6 indicates the magnitude of performance improvement that can be achieved by using more advanced recycler configurations that provide higher region-specific values.
As the loss in the bed decreases, the heat that must be rejected will decrease, so the loss associated with the heat exchanger is also large, as shown in Figure 6, which can be indirectly reduced.
Cold and heat exchangers for refrigeration applications are modeled using the same method as previously described
Cooling application.
Condensation and Frost are not considered when modeling Cold Heat Exchangers in refrigeration applications.
This model is used to predict the reaction performance at the freezing temperature. Gan (1998)
150 W residential Research (500 Btu/h)
Refrigerator/freezer with split refrigerator and refrigerator circulation.
The conductivity of the AMRR heat exchanger is considered to be the sum of the conductivity of the refrigerator and refrigerator condenser, and the conductivity of the hot and cold exchanger is the sum of the conductivity of the heat exchanger and the frozen evaporator of the household refrigerator/freezersystem.
Table 3 summarizes the specific heat exchanger parameters and other model inputs used for the analysis.
Figure 7 shows the predicted COPs as a function of the volume of the recycler of the layered and non-layered beds;
These curves are generated using a cooling capacity of 150 W and an optimal volume ratio and mass flow rate for each volume.
Fan power is a small part of the input power for refrigeration applications and is ignored in this analysis. From Jaehnig (1999)
The COP of a typical evaporation compression system operating under these conditions is about 1. 9.
The comparison between Figure 7 and Figure 4 shows that the effect of the regeneration bed stratification of the AMRR system on its refrigeration application performance is more influential than its space.
Cooling application performance.
The result of this behavior is that the increased temperature of the refrigeration application results in the regeneration material in the non-layered bed being further away from its dwell point temperature;
Therefore, it exhibits a relatively low magnetic thermal effect.
In contrast, the material in the layered bed is selected so that the local temperature is always close to the dwell point temperature of the material at the position of the recycler.
For refrigeration applications, non-layered beds cannot achieve COP that competes with the current evaporation compression technology, while layered beds can exceed the evaporation compression performance by using a large enough regeneration bed. [
Figure 7 Slightly]
Conclusion the numerical model proposed in this paper can predict the performance of the AMRR system with hierarchical Regeneration Matrix.
Refrigeration and refrigeration applications.
This model is used to analyze the influence of mass flow, aspect ratio, generator volume under the background of gd and er co-distributed sphere matrix.
The model is in aspace-
Cooling and refrigeration applications show that if the volume of the recycler is very large, the COP of the properly designed AMRR system can be comparable to the current vapor pressure technology.
Confirmation financial support for the project is provided by the airline
Institute of air conditioning and refrigeration technology (ARTI)
Agrant by the American Association of heating and air
Condition engineer.
The technical assistance of the Space Corporation and the personnel of the ARTI 21CR Emerging Technologies subcommittee was appreciated. NOMENCLATURE [A. sub. c]= cross-
Section area of heat storage bed ,[m. sub. 2][a. sub. s]
= Surface area density of regenerative beds ,[m. sub. 2]/[m. sub. 3]
Heat transfer coefficient of convection, W /[m. sub. 2]x K [h. sub. aug]
= Heat transfer coefficient of enhanced convection, W /[m. sub. 2]x K [h. sub. eff]
= Effective heat transfer coefficient of generator, W /[m. sup. 2]
X k l = length, m [dot. m]
= Mass flow rate, kg/s M = magnetic field strength, A/m N torque, N/m accept Kurt L April 17, 2006
Engel Brecht is a graduate student, Greg F.
Naris is an assistant professor and Sandford is an assistant professor.
Klein is a professor of mechanical engineering at the University of Wisconsin.
Madison, Madison, WI.
* Measured data at Ames labs, Ames, IA and provided by Aerospace, Madison, WI.
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