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Title: A novel radio frequency assisted heat pump dryer

Abstract

This paper compares an experimental heat pump batch dryer with the implementation of volumetric Radio Frequency (RF) heating, in the combination drying of crushed brick particulate. Results are presented showing overall improvements in drying. A simplified mathematical drying model including the RF energy source has been developed using mass and energy conservation, confirming the experimental results. Drying is a widespread, energy intensive industrial unit operation. The economics of a drying process operation largely depend upon the dryers performance and ultimately the cost of energy consumption. To enhance the performance of a drying system, the damp air stream that exits the drying chamber can be recycled to reclaim the enthalpy of evaporation that it carries, by using a heat pump (Hodgett, 1976). However, because the medium that dries is still warm air, this system also suffers from heat transfer limitations, particularly towards the falling drying rate period. Such limitations in drying performance can be overcome with the use of Radio Frequency (RF) energy which generates heat volumetrically within the wet material by the combined mechanisms of dipole rotation and conduction effects which speeds up the drying process (Metaxas et al, 1983). Despite the clear advantages that heat pumps and high frequencymore » heating offer for drying, the combination of these two techniques until recently has not been studied (Kolly et al, 1990; Marshall et al, 1995).A series of experiments carried out comprising a motor driven heat pump which was retro-fitted with the ability of imparting RF energy into a material at various stages of the drying cycle are described and compared with a mathematical model.« less

Authors:
;
Publication Date:
Research Org.:
Univ. of Cambridge (GB)
OSTI Identifier:
20006237
Resource Type:
Journal Article
Journal Name:
Drying Technology
Additional Journal Information:
Journal Volume: 17; Journal Issue: 7-8; Conference: 11th International Drying Symposium (IDS'98), Halkidiki (GR), 08/19/1998--08/22/1998; Other Information: PBD: Aug-Sep 1999; Journal ID: ISSN 0737-3937
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; DRYERS; HEAT PUMPS; DESIGN; PERFORMANCE; AUGMENTATION; RF SYSTEMS; MATHEMATICAL MODELS

Citation Formats

Marshall, M G, and Metaxas, A C. A novel radio frequency assisted heat pump dryer. United States: N. p., 1999. Web. doi:10.1080/07373939908917636.
Marshall, M G, & Metaxas, A C. A novel radio frequency assisted heat pump dryer. United States. https://doi.org/10.1080/07373939908917636
Marshall, M G, and Metaxas, A C. 1999. "A novel radio frequency assisted heat pump dryer". United States. https://doi.org/10.1080/07373939908917636.
@article{osti_20006237,
title = {A novel radio frequency assisted heat pump dryer},
author = {Marshall, M G and Metaxas, A C},
abstractNote = {This paper compares an experimental heat pump batch dryer with the implementation of volumetric Radio Frequency (RF) heating, in the combination drying of crushed brick particulate. Results are presented showing overall improvements in drying. A simplified mathematical drying model including the RF energy source has been developed using mass and energy conservation, confirming the experimental results. Drying is a widespread, energy intensive industrial unit operation. The economics of a drying process operation largely depend upon the dryers performance and ultimately the cost of energy consumption. To enhance the performance of a drying system, the damp air stream that exits the drying chamber can be recycled to reclaim the enthalpy of evaporation that it carries, by using a heat pump (Hodgett, 1976). However, because the medium that dries is still warm air, this system also suffers from heat transfer limitations, particularly towards the falling drying rate period. Such limitations in drying performance can be overcome with the use of Radio Frequency (RF) energy which generates heat volumetrically within the wet material by the combined mechanisms of dipole rotation and conduction effects which speeds up the drying process (Metaxas et al, 1983). Despite the clear advantages that heat pumps and high frequency heating offer for drying, the combination of these two techniques until recently has not been studied (Kolly et al, 1990; Marshall et al, 1995).A series of experiments carried out comprising a motor driven heat pump which was retro-fitted with the ability of imparting RF energy into a material at various stages of the drying cycle are described and compared with a mathematical model.},
doi = {10.1080/07373939908917636},
url = {https://www.osti.gov/biblio/20006237}, journal = {Drying Technology},
issn = {0737-3937},
number = 7-8,
volume = 17,
place = {United States},
year = {Wed Sep 01 00:00:00 EDT 1999},
month = {Wed Sep 01 00:00:00 EDT 1999}
}