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United States Department of Agriculture

Agricultural Research Service

Title: Pulse Jet Orchard Heater System Development: Part I: Design, Construction and Optimization

Authors
item Evans, Robert
item Alshami, Ali - WASHINGTON STATE UNIV

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 12, 2009
Publication Date: April 30, 2009
Repository URL: http://hdl.handle.net/10113/30505
Citation: Evans, R.G., Alshami, A.A. 2009. Pulse Jet Orchard Heater System Development: Part I: Design, Construction and Optimization. Transactions of the ASABE. 52(2): 331-343.

Interpretive Summary: The design, development and optimization of an efficient and effective orchard heater system that is environmentally friendly and economically competitive are presented. These new generation orchard heaters are stationary, auto-regulating, horizontal pulse jet engines (combustors) with no moving parts. They utilize air ejector technology to reduce the temperature of the high velocity combustion stream by thoroughly mixing it with the surrounding ambient (cold) air, producing a net effective temperature increase of only 2-4°C above ambient. Buoyant forces of warm air are therefore small and fewer heaters would be needed. The design achieved pressure oscillations that were free of combustion instabilities and amplitudes were maximized for high exhaust jet velocities for deep hot jet penetration and mixing into the surrounding cold air. The overall size and weight of the heater system were minimized while maintaining optimum operation. Finally, anti-phase operation of paired heaters for noise level reduction from 130 db to near 75 db was achieved by implementing optimized silencing plenums at the inlet and exhaust of the paired heaters.

Technical Abstract: The design, development and optimization of an efficient and effective orchard heater system that is environmentally friendly and economically competitive are presented. These new generation orchard heaters are stationary, auto-regulating, horizontal pulse jet engines (combustors) with no moving parts. They utilize air ejector technology to reduce the temperature of the high velocity combustion stream by thoroughly mixing it with the surrounding ambient (cold) air, producing a net effective temperature increase of only 2-4°C above ambient. Buoyant forces of warm air are therefore small and fewer heaters would be needed. The design achieved pressure oscillations that were free of combustion instabilities and amplitudes were maximized for high exhaust jet velocities for deep hot jet penetration and mixing into the surrounding cold air. The overall size and weight of the heater system were minimized while maintaining optimum operation. Finally, anti-phase operation of paired heaters for noise level reduction from 130 db to near 75 db was achieved by implementing optimized silencing plenums at the inlet and exhaust of the paired heaters.

Last Modified: 10/1/2014
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