Regenerative heat exchangers with significant entrained fluid heat capacity

Nellis, Gregory; Klein, S.A.

doi:10.1016/j.ijheatmasstransfer.2005.06.021

Cited by 30 publications

(9 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a result, the entrained fluid heat capacity should not be neglected when modeling an AMRR system. Nellis and Klein (2004) developed a method to correct for the lumped capacitance assumption used to derive the regenerator model; that is, the combining of the fluid and regenerator heat capacity in the governing equations.…”

Section: Correction For Entrained Fluid Heat Capacitymentioning

confidence: 99%

A Numerical Model of an Active Magnetic Regenerator Refrigeration System

2005

View full text Add to dashboard Cite

Active magnetic regenerator refrigeration (AMRR) systems are an environmentally attractive space cooling and refrigeration alternative that do not use a fluorocarbon working fluid. Two recent developments have made AMRRs appear possible to implement in the near-term. A rotary regenerator bed utilizing practical and affordable permanent magnets has been demonstrated to achieve acceptable COP. Concurrently, families of magnetocaloric material alloys with adjustable Curie temperatures have been developed. Using these materials it is possible to construct a layered regenerator bed that can achieve a high magnetocaloric effect across its entire operating range, resulting in an improved COP.There is currently no tool capable of predicting the performance of a layered AMRR. This project provides a numerical model that predicts the practical limits of these systems for use in space conditioning and refrigeration applications. The model treats the regenerator bed as a one dimensional matrix of magnetic material with a spatial variation in Curie temperature and therefore magnetic properties. The matrix is subjected to a spatially and temporally varying magnetic field and fluid mass flow. The variation of these forcing functions is based on the implementation of a rotating, multiple bed configuration. The numerical model is solved using a fully implicit (in time and space) discretization of the governing energy equations. The nonlinear aspects of the governing equations (e.g., fluid and magnetic property variations) are handled using a relaxation technique.The model is used to optimize AMRR applications by varying model inputs such as matrix material, fluid mass flow rate, working fluid, reservoir temperatures, and the variation of the Curie temperature across the bed. The preliminary model has been verified qualitatively using simple cycle parameters and constant property materials and quantitatively by comparing the results with prior solutions to the regenerator governing equations in the limits of constant properties and no magnetocaloric effect. A second goal of this project is to create a cost estimate for a future project that will design, build, and test a prototype AMRR to be used to verify the numerical model.

show abstract

Section: Correction For Entrained Fluid Heat Capacitymentioning

confidence: 99%

A Numerical Model of an Active Magnetic Regenerator Refrigeration System

2005

View full text Add to dashboard Cite

show abstract

“…Several assumptions applied in conventional passive regenerator models are not valid for AMRs. The heat transfer fluid in AMRs is usually a liquid so its heat capacity is not negligible (Nellis and Klein, 2006). The thermal conductivity of typical MCMs such as gadolinium is also significant (Nielsen and Engelbrecht, 2012).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

An efficient numerical scheme for the simulation of parallel-plate active magnetic regenerators

Torregrosa-Jaime

Corberán

Payá

et al. 2015

International Journal of Refrigeration

View full text Add to dashboard Cite

A one-dimensional model of a parallel-plate active magnetic regenerator (AMR) is presented in this work. The model is based on an efficient numerical scheme which has been developed after analysing the heat transfer mechanisms in the regenerator bed. The new finite difference scheme optimally combines explicit and implicit techniques in order to solve the one-dimensional conjugate heat transfer problem in an accurate and fast manner while ensuring energy conservation. The present model has been thoroughly validated against passive regenerator cases with an analytical solution. Compared to the fully implicit scheme, the proposed scheme achieves more accurate results, prevents numerical errors and requires less computational effort. In AMR simulations the new scheme can reduce the computational time by 88%.

show abstract

“…Based on the above assumptions, an energy balance for the secondary fluid and for the magnetic material can be performed and the following equations in general form can be obtained:

{\begin{cases} m_{f} c_{f} \frac{\partial T_{f}}{\partial normalt} + {\dot{normalm}}_{f} normalL c_{f} \frac{\partial T_{f}}{\partial normalx} - {(A . K .)}_{f} = normalh A_{SC} {(normalT}_{s} - T_{f}) + ((), \frac{\partial p}{\partial x}) \frac{{\overset{m}{true}}_{f}}{ρ_{f}} L \\ m_{s} c_{s} \frac{\partial T_{s}}{\partial normalt} - {(A . K .)}_{s} = normalh A_{SC} {(normalT}_{f} - T_{s} {)‐ normalm}_{s} T_{s} {(\frac{\partial s_{s}}{\partial H})}_{T} ((), \frac{\partial H}{\partial t}) \end{cases}

…”

Section: Modelling Of Amr Cyclementioning

confidence: 99%

A dimensionless numerical analysis for the optimization of an active magnetic regenerative refrigerant cycle

Aprea

Greco

Maiorino

2012

Int. J. Energy Res.

View full text Add to dashboard Cite

SUMMARY Refrigeration by an active magnetic regenerative system (AMR) is potentially more attractive, as compared to conventional techniques. Indeed, devices based upon an AMR cycle are more efficient, compact, environment‐friendly and can operate over a broad range of temperatures. In this paper, attention is focused to the near room‐temperature range. On the other hand, however, the AMR cycle poses a variety of complex problems, in terms of fluid dynamics, heat transfer and magnetic field. In order to identify the optimal operational parameters, the design and optimization of a magnetic refrigeration system can be supported by modelling. In this paper, a dimensionless approach was adopted to simulate an AMR cycle following a Brayton regenerative cycle. In the simulation, the temperature range that has been explored is 260 – 280 K and 275 – 295 K. The heat transfer mediums are, respectively, water–glycol mixture (50% by weight) and pure water. The Gd0.8Dy0.2 alloy and pure Gd have been chosen as constituent material for the regenerator of the AMR cycle. With this model, the influence of the different parameters on cycle efficiency has been analysed. In particular, the study has been focused on the influence of the secondary fluid properties, magnetic material particle diameter, fluid blow time, secondary fluid mass flow rate, regenerator geometry and effect of axial thermal conduction. The model enables to find optimal dimensionless numbers in order to maximize the cycle performances. The results can be extended to widely different situations and therefore can be easily employed for the design and the optimization of new experimental prototypes. Copyright © 2012 John Wiley & Sons, Ltd.

show abstract

Regenerative heat exchangers with significant entrained fluid heat capacity

Cited by 30 publications

References 11 publications

A Numerical Model of an Active Magnetic Regenerator Refrigeration System

A Numerical Model of an Active Magnetic Regenerator Refrigeration System

An efficient numerical scheme for the simulation of parallel-plate active magnetic regenerators

A dimensionless numerical analysis for the optimization of an active magnetic regenerative refrigerant cycle

Contact Info

Product

Resources

About