Impact of Component Selection and Operation on Thermal Ratings of Drain-Back Solar Water Heaters

Davidson, Jane H.; Carlson, W. T.; Duff, William S.

doi:10.1115/1.2930009

Cited by 11 publications

(9 citation statements)

References 3 publications

(5 reference statements)

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“…Kleinbach (1990;Kleinbach, et al, 1991) investigated experimental data for the eight (out of 16) trials without a stratification manifold and concluded that a multimode model, which models the tank as N fully mixed volume segments, predicts tank temperatures and energy delivery better Carlson (1990) and Davidson et al (1992).) Of particular interest are the differences in energy quantities Qu, Qs, Q 0 • 1 , and Qaux· Both the experimental and simulated trials deliver the correct total energy to the load.…”

Section: Journal Of Solar Energy Engineeringmentioning

confidence: 99%

“…A schematic diagram of a generic drain-back system is shown in Fig. 2. (A detailed description of the system is included in Davidson et al, 1992. ) Water is the working fluid throughout the system.…”

Section: Journal Of Solar Energy Engineeringmentioning

confidence: 99%

“…An alternate, and more cost-effective rating methodology now relies heavily on computer simulations (SRCC, 1991). To determine the validity of the simulation certification path, experimental ratings of generic drain-back systems (Davidson et al, 1992) are compared with simulated ratings obtained with TRNSYS 13.1 (Klein et al, 1990).…”

Section: Introductionmentioning

confidence: 99%

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Comparison of Experimental and Simulated Thermal Ratings of Drain-Back Solar Water Heaters

Davidson

Carlson

Duff

et al. 1993

Journal of Solar Energy Engineering

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Section: Journal Of Solar Energy Engineeringmentioning

confidence: 99%

Section: Journal Of Solar Energy Engineeringmentioning

confidence: 99%

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Comparison of Experimental and Simulated Thermal Ratings of Drain-Back Solar Water Heaters

Davidson

Carlson

Duff

et al. 1993

Journal of Solar Energy Engineering

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“…2, is a rigid porous manifold constructed of 8.9-cm diameter PVC pipe with both vertical and horizontal resistance elements. Details of the manifold design are given in Carlson (1990) and Davidson et al (1992). The manifold includes a momentum diffuser to reduce the vertical component of momentum of water entering the tank and a distribution manifold with vertical orifice plates which reduce plume entrainment by forcing fluid to exit at the vertical height where the temperature of the fluid entering the tank equals the temperature of the fluid in the tank.…”

Section: Experimental Validationmentioning

confidence: 99%

“…The extent of natural convection is a function of the temperature of the incoming fluid, the temperature distribution within the tank, and the design and location of the inlet. Porous distribution manifolds have been tested which allow the fluid to enter the tank to an appropriate level with reduced mixing (Sharp and Loehrke, 1979;Loehrke et al, 1979;Davidson et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

A Coefficient to Characterize Mixing in Solar Water Storage Tanks

Davidson

Adams

Miller

1994

Journal of Solar Energy Engineering

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IntroductionExperimental (Davis and Bartera, 1975;Lavan and Thompson, 1977;Fanney and Klein, 1988) and analytical (Sharp and Loehrke, 1979;Wuestling, 1983 ;Jesch and Braun, 1984;Wuestling et al., 1985) investigations show that thermal stratification of the solar storage tank enhances the performance of solar domestic hot water (SDHW) systems . Maximum possible thermal performance is obtained when no mixing occurs in the solar storage tank. In this case, the coldest stored fluid is circulated through the collector(s). Heated water is then returned to the tank without inducing mixing of fluid layers with different temperatures. During water draws to the load, the hottest water in the tank is withdrawn from the tank and replaced (again without mixing) with cold water from the mains water supply. Minimum performance is obtained when fluid streams entering the storage tank mix completely (and instantaneously) with water in the tank . In this case, water circulated to the collector is at the same temperature as that supplied to the load.Loss of stratification of the thermal storage tank results from convective mixing, both forced and natural , and, to a lesser extent, from conduction between hot and cold fluid layers. Maintaining thermal stratification requires inhibition of mixing in the tank. Mixing depends on the design of the tank and the operating conditions (flow rate and temperature of incoming fluid streams and the temperature distribution in the tank). Forced convection mixing is due to the momentum of the fluid streams entering the storage tank and depends on the flow rate of the entering stream and the design of the inlet. Momentum diffusers have been employed to reduce mixing due to jet entrainment.

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Drain Back Systems in Laboratory and in Practice

et al. 2015

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Drain Back systems with ETC collectors are tested and analyzed in a Danish -Chinese cooperation project. Experiences from early work at DTU, with drain back, low flow systems, was used to design two systems: 1) One laboratory system at DTU. 2) One demonstration system in a single family house in Sorö Denmark. Detailed monitoring and modelling/validation of the system in the DTU lab is done, to be able to generalize the results, to other climates and loads by simulation and to make design optimizations. The advantage with drain back, low flow systems, is that the system can be made more simple with less components and that the performance can be enhanced. Also problems with long term degradation of glycol collector loops are totally avoided. A combination of the drain back and system expansion vessel was tested successfully. It is very important to achieve a continuous slope for the pipes in the collector loop to have a safe reliable operation. The components should also be designed and marked so that only one correct mounting option is possible, like forward and return pipes to/from the collector of slightly different sizes or color. Adapted installer education and training is a very important step to have success with drain back systems. Practices used in glycol systems may give serious failures.

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Impact of Component Selection and Operation on Thermal Ratings of Drain-Back Solar Water Heaters

Abstract: A half-factorial, two-level experimental design is used to determine the effects of changes in collector area

Cited by 11 publications

References 3 publications

Comparison of Experimental and Simulated Thermal Ratings of Drain-Back Solar Water Heaters

Comparison of Experimental and Simulated Thermal Ratings of Drain-Back Solar Water Heaters

A Coefficient to Characterize Mixing in Solar Water Storage Tanks

Drain Back Systems in Laboratory and in Practice

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