Enhancing the thermosiphon-driven discharge of a latent heat thermal storage system used in a personal cooling device

Dhumane, Rohit; Mallow, Anne; Qiao, Yiyuan; Gluesenkamp, Kyle R.; Graham, Samuel; Ling, Jiazhen; Radermacher, Reinhard

doi:10.1016/j.ijrefrig.2018.02.005

Cited by 15 publications

(12 citation statements)

References 59 publications

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“…All the properties of PCM required for the model are not available experimentally. As a result, properties of a PCM with similar graphite concentration from an earlier study (Dhumane et al, 2018) is used. These properties are given in Table 1.…”

Section: Resultsmentioning

confidence: 99%

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Modeling Heat Pump Recharge of a Personal Conditioning System with Latent Heat Storage

Dhumane

Ling

Aute

et al. 2019

Linköping Electronic Conference Proceedings

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Roving Comforter provides personal cooling in the range of 150 W using vapor compression cycle (VCC) up to 4 hours. During this operation, the condenser heat is stored in a latent heat storage made of phase change material (PCM). This heat needs to be discharged before next cooling operation. A heat pump mode is considered and analyzed for this heat discharge in the present article. The cycle is modeled using CEEEModelicaLibrary, which is a commercial package for complex vapor compression systems. Equations and assumptions involved in modeling some of the components is presented. Programming and modeling decisions for PCM modeling are discussed in detail. A parametric study is conducted with the heat pump system model to identify merits and demerits of operating heat pump cycle at various compressor RPM's.

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Section: Resultsmentioning

confidence: 99%

“…The first prototype (Dhumane et al, 2019) used paraffin based phase change material for latent heat storage. For recharge operation, a thermosiphon operation was used (Dhumane et al, 2018). The technology can provide annual energy savings per person up to $130 (Heidarinejad et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Modeling Heat Pump Recharge of a Personal Conditioning System with Latent Heat Storage

Dhumane

Ling

Aute

et al. 2019

Linköping Electronic Conference Proceedings

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“…The refrigerant circuit of RoCo using thermosiphon for recharge involves two ball valves, which by-pass the compressor and expansion device from the refrigerant circuit for cooling cycle. Details of this thermosiphon operation is available in Dhumane et al (2018) and omitted here for brevity. As discussed in Dhumane et al (2018) the recharge time of the thermosiphon can be significantly enhanced by addition of graphite to the phase change material (PCM).…”

Section: System Descriptionmentioning

confidence: 99%

“…The PCM stores heat from the condenser as it melts and thus its latent heat of melting limits the cooling operation period for RoCo. A two-phase thermosiphon Dhumane et al (2018) is used to re-solidify the PCM before its next operation.…”

Section: Introductionmentioning

confidence: 99%

Evaluating Recharge Options for Phase-Change Material Storage of a Personal Conditioning System

Dhumane

Qiao

Muehlbauer

et al. 2019

Science and Technology for the Built Environment

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Buildings consume about two-fifths of the primary energy in the United States with space heating and cooling taking up one-third of that fraction. Global warming and the associated climate changes have necessitated a rethinking of our energy consumption patterns. Roving Comforter (RoCo) is one such technology being developed with this objective. It enables buildings to save 10-30% of HVAC (Heating, Ventilating, and Air Conditioning) loads by enabling elevation of temperature set-points without compromising occupant comfort. The cooling operation involves an R134a vapor compression cycle operation, which stores the condenser heat into a phase change material (PCM) based thermal storage. Previous studies focused on enhancing the PCM to reduce the recharge time by thermosiphon operation from 8 hours for non-enhanced version by 40% without a significant increase in the weight of the thermal storage. This enhanced PCM storage needs to be recharged before the next cooling operation, which may be conducted in two different ways. A gravity-assisted two-phase thermosiphon operation consumes very less power takes a longer recharge time (6.5 hours) in comparison to a reverse heat pump operation which consumes more power in a much shorter operation time (2.5 hours). The current article uses a validated dynamic model of thermosiphon and heat pump in Modelica to evaluate the overall coefficient of performance for combined cooling and recharge operations. Reduced recharge time from the heat pump recharge leads to increased frequency of the cooling operation enabling savings on building HVAC energy. All these factors are considered in making design recommendations for future prototypes of RoCo, which will save additional energy and provide longer cooling operation to the current prototypes. The modeling framework discussed in the article being generic may be used by researchers investigating vapor compression cycle integration strategies with PCM thermal storages. The article provides interesting insights and quantification of benefits obtained from various strategies adopted for improvement over the first prototype.

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“…The application of two-phase (liquid and vapor) thermosiphon is generally wider. It is also used in nuclear systems [24] but in addition, it can be used in the cooling of super-conductors [24], thermal diodes [25], gas turbines [26] or in electronics cooling [16], latent heat thermal storage systems [27], household refrigerator applications [28] and as distillation column reboilers [29]. Reverse two-phase thermosiphons have great potential to operate in solar installations [30] (heat source situated above the heat sink) but due to technical imperfections, these devices have not yet found a wide practical application.…”

Section: Introductionmentioning

confidence: 99%

Flow Boiling in Minigap in the Reversed Two-Phase Thermosiphon Loop

2019

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The paper presents the results of experimental investigations of a model of a heat exchanger featuring a minigap, which is perceived as an evaporator for an inverted thermosiphon. The system works with a single component test fluid. The tested evaporator generates pumping power in the test loop in a way similar to the mammoth pump. The tests regarded a module of the heat exchanger, consisting of a hot leg and a cold leg with the width by the length of 0.1 × 0.2 m, heated by a uniform heat flux. In the tests, the minigaps of 1, 2 and 3 mm were formed. Two fluids, namely, distilled water and ethanol, were tested in the facility. Two-phase flow structures for both working fluids and various operational parameters, together with comprehensive visualization material, are presented. The specifics of pressure changes and its influence on operating parameters and flow structure are discussed.

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Enhancing the thermosiphon-driven discharge of a latent heat thermal storage system used in a personal cooling device

Cited by 15 publications

References 59 publications

Modeling Heat Pump Recharge of a Personal Conditioning System with Latent Heat Storage

Modeling Heat Pump Recharge of a Personal Conditioning System with Latent Heat Storage

Evaluating Recharge Options for Phase-Change Material Storage of a Personal Conditioning System

Flow Boiling in Minigap in the Reversed Two-Phase Thermosiphon Loop

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