Experimental evaluation of solar thermosyphons with heat exchangers

Abstract

In keeping with the national energy policy goal of fostering an adequate supply of energy at a reasonable cost, the United States Department of Energy (DOE) supports a variety of programs to promote a balanced and mixed energy resource system. The mission of the DOE Solar Buildings Research and Development Program is to support this goal, by providing for the develop-o ment of solar technology alternatives for the buildings sector. It is the goal of the program to establish: a proven technology base to allow industry to develop solar products and designs for buildings which are economically competitive and can contribute significantly to building energy supplies nationally.· Toward this:. end; the program. sponsors research actiYities'. related to increasing~.the efficiency, reducing-the cost; and improving:the long-term durability of passive and active solar systems{or build,ing·water and space heating, cooling, and daylighting applica". tions. These activities are conducted in four major areas: Advanced Passive Solar Materials Research, Collector Technology Research, Cooling Systems Research, and Systems Analysis and Applications Research. Advanced Passive Solar MaterialsResearch. This activity area includes work on new aperture materials for controlling solar heat gains, and for enhancing the use of daylight for building interior lighting purposes. lt also encompasses work on lowocost thermal storage materials that have high thermal . . storage capacity. and can. be. integrated with conven tiona! building elements, and work on materials and methods to transport thermal energy efficiently between any. building exterior surface,and the building interior by nonmechanical means. Collector· TechnologyResearch. This activity area encompasses work on advanced low-to-. medium temperature (up to 180 • F useful operating temperature) fiat plate collectors for water and space heating applications, and medium-: to-high temperature (up to 400 • F useful operating· temperature) evacuated tube/concentrating collectors· for space heating and cooling applications. The focus is on design innovations using new materials and fabrication techniques.Cooling Systems Research. This activity area involves research on high performance dehumidifiers and chillers that can operate efficiently with the variable thermal outputs and delivery temperatures associated with solar collectors. It also includes work on advanced passive cooling techniques. Systems Analysis and Applications·Research. This activity area encompasses experimental test• ing; analysis; and evaluation of solar heating·, cooling,· and daylighting systems for residential and nonresidential buildings. Th'is· involves<; system integration studies, the~ development of. design and analysis tools, and the establishment of overall cost, performance, and durability targets:f or'various ctechnolo·gy or"system ·\o·ptibns.This report is an account of research conducted in SystemsAnalysis and Applications concerning experimental testing of solar thermosyphons for residential hot water...

Development and Evaluation of a Solar Milk Pasteurizer for the Savanna Ecological Zone of West Africa

“…Only visible light and shortwavelength infrared radiation pass through the glass. The glass is opaque to long-wavelength infrared radiation [28,29]. On reaching the flat plate, the metal absorbs the incident energy, heating to a relatively lower temperature.…”

“…The hot water vat conducts heat to the milk vat, which also conducts heat to the milk, there raising the milk temperature. This process is known as thermosiphon circulation [28,29]. The process continues until the milk reaches pasteurization temperatures between 65 °C and 72 °C.…”

“…This process continues until the milk is heated to 60 °C and 75 °C. This process is known as thermosiphon circulation [28,29].…”

Improving thermosyphon solar domestic hot water system model performance. Final report, March 1994--February 1995

“…Rakopoulos and Vazeos (1986) collected data on a system with an internal horizontal tube heat exchanger and describe a model that predicts performance fairly well, but they do not compare performance to a similar system without a heat exchanger. Webster et al (1987) derived a "heat exchanger penalty fkctof' for a system with a horizontal tank and a multi-horizontal-tube heat exchanger and found significant performance degradations, likely due to reduced stratification in the horizontal tank due: to the type of heat exchanger used in the study. They concluded that a relatively large heat transfer area may be required.…”