Observational study of modified solar still coupled with oil serpentine loop from cylindrical parabolic concentrator and phase changing material under basin

Solar still is one of the economic and eminent ways of desalinating the available sea/brackish water into potable water. However, the distillate output from the solar still is moderate and various researches are being conducted to improve the productivity of solar still. In this research, a novel bottom finned (solid and hollow) absorber basin is designed and developed to enhance the heat transfer between absorber and phase change material (PCM) which further improves the freshwater productivity from the solar still. The results of the investigation are compared with the conventional solar still. The three single-slope solar stills considered developed for evaluating the effect of modification on the freshwater productivity are (i) conventional solar still (CSS), (ii) solar still with hollow finned absorber inserted in energy storage (SSHFES), and (c) solar still with solid finned absorber inserted in energy storage (SSSFES). The investigation results reported that the SSHFES has greater productivity when compared with the SSSFES and CSS. The freshwater productivity from the SSHFES is 4085 mL/m2 day, whereas the freshwater productivity from SSSFES and CSS is 3485 mL/m2 day and 2885 mL/m2 day, respectively. The efficiency of SSHFES and SSSFES is increased by 41.67% and 20.81% relative to the CSS. It is observed from economic analysis that the cost per liter (CPL) freshwater produced by SSHFES, SSSFES and CSS is about ₹ 2.3 ($ 0.032), ₹ 2.5 ($ 0.034), and ₹2.6 ($ 0.036), respectively. The payback periods of SSHFES, SSSFES, and CSS is 6.3 months, 6.8 months, and 7.1 months, respectively. Also, the enviroeconomic analysis conferred that the carbon credit gained from the SSHFES is $189.28 whereas SSSFES and CSS gained only $158.2 and $132.02. Based on the current study, it is observed that the solar still with hollow finned absorber inserted in energy storage (SSHFES) is effective when compared to others and it is viable for potable water production at cheaper costs.

The objective of this research work is to evaluate the influence of v-shaped corrugated basin integrated with nano-enhanced phase change material (NePCM) on the freshwater productivity. Experiments were conducted using different nanoparticles such as graphene oxide (GO), Al2O3, TiO2 and CuO as well as phase change material (PCM) namely fatty acids and graphene oxide. The conventional single slope solar still (CSSS) was combined with individual nanoparticles (CSSS + nanoparticle) and PCM (CSSS + PCM) and also with their combination (CSSS + nanoparticle + PCM) for performance analysis. The consideration of nanoparticle and PCM either individually or in combination increased the daily yield in comparison to the CSSS. The highest productivity was obtained in the case of CSSS + Paraffin wax + Al2O3 + TiO2 + GO (5.21 L/m2/day) as compared to the CSSS (3.15 L/m2/day), increasing the daily yield by 65%. The daily yield in case of CSSS + Fatty acid + Al2O3 + TiO2 + GO is 5.09 L/m2/day over the CSSS, thereby resulting in productivity improvement by 61%. The findings of the study present the potentiality of the developed v-shaped corrugated solar still with different combination of nanoparticles and PCM.

An Improvement in the Solar Water Heating Systems by Thermal Storage Using Phase Change Materials

Mathematical modeling for transient thermal performance analysis of phase change material-based heat exchanger

Employing phase change materials (PCMs) for latent heat storage (LHS) application has a great potential to improve a solar thermal system performance. Despite this fact, the use of PCM in this area is quite limited due to the poor thermal conductivity of available PCMs. Therefore, heat transfer enhancement is one of the essential strategies that can overcome this obstacle. In this paper and related project, a PCM heat exchanger (HX) is purposely designed with spiral-wired tubes and integrated in an indirect solar assisted heat pump test system. Although the spiral-wired tube has not been applied in a PCM HX, it is expected to enhance significantly the PCM heat transfer and heat storage performance. To verify this and understand the PCM heat storage and releasement processes, a detailed 3D CFD model has been developed for the PCM HX and validated with measurements. The temperature variations and visualizations of the PCM during charging and discharging processes are therefore simulated and presented temporally. Furthermore, the effects of different inlet heat transfer fluid flow rates and temperatures on the PCM melting/solidification time are demonstrated in this study. Some significant simulation results have been obtained which can instruct efficiently the operation of the heat exchanger and its integration with the solar system.

Thermal energy storage with phase change materials (PCMs) has attracted a lot of attention in the last several decades. Most PCMs do not change phase at a constant temperature but rather in a certain temperature range. It means that the PCM need to transit through its phase change temperature range to fully change phase from the solid state to the liquid state and vice-versa. The situation, in which the phase transition begins and/or ends within the phase change temperature range (in the mushy zone), is usually called a partial phase transition (or a partial phase change). The partial phase transitions occur quite often in real-life thermal energy storage systems with PCMs; especially when a PCM has a wide phase change temperature range. The behavior of PCMs during the partial phase transitions is poorly understood at the moment, because the experimental techniques used for the characterization of PCMs (such as the differential scanning calorimetry – DSC) are difficult to apply for the study of partial phase transitions. The lack of knowledge in this area influences the accuracy of phase change simulation models. The main goal of the experimental investigations, described in the paper, was to obtain data for the development of a simulation model for partial phase changes. The experimental set up for the investigation of partial phase changes of PCMs has been proposed, assembled, and the pilot measurements have been conducted. The experimental set up consists of two water storage tanks (that can be maintained at different water temperatures), a water-PCM concentric tube type heat exchanger and a data acquisition system. The water flows through the central tube of the heat exchanger while the PCM is located in the annular space of the exchanger. The water storage tanks, maintained at the temperatures within the phase change temperature range of a PCM, allow for the investigations of the heat storage cycles consisting of partial phase changes.

Heat storage process analysis in a heat exchanger containing phase change materials

High power density thermal energy storage using additively manufactured heat exchangers and phase change material

PCM–air heat exchangers for free-cooling applications in buildings: Experimental results of two real-scale prototypes

This chapter discusses the application of ultrahigh temperature thermal energy storage (TES) and conversion to spacecraft systems. The use of silicon and boron as phase change materials (PCMs) is of primary interest for spacecraft in the context of a thermal rocket. The history of this concept is discussed as applied to solar thermal propulsion and dual-use radioisotope propulsion and power systems. In both the cases the use of high-temperature PCMs as a primary thermal capacitor has been frequently cited as beneficial, but investigations seldom go beyond the conceptual phase. For solar thermal propulsion, the inclusion of PCMs can drastically decrease the volume and mass of a propulsion system, provided that effective convective coupling to the PCM is achieved in the heat exchanger. However, the benefits of solar thermal propulsion have historically been relegated to niche mission scenarios. The more compelling application of ultrahigh temperature PCMs is in a pulsed radioisotope propulsion and power system where it is a truly enabling technology offering both high specific energy and power. It is suggested that future development efforts would focus on characterizing convective coupling to a latent heat storage medium since all applications require some form of heat exchange with a working fluid. A meaningful mission design cannot just look at material properties and must include effective energy transfer for an optimized heat exchanger to determine the net system benefit. Ultimately, this chapter highlights benefits that can be obtained by latent heat TES but cautions that the ultimate benefit to a spacecraft system is mission-dependent and will rely on a distinct mission need for a high specific power and energy system to justify technological investment.

Thermal storage analysis of a foam-filled PCM heat exchanger subjected to fluctuating flow conditions

Investigation of numerical and experimental assessment of melting behavior of phase change material in U tube heat exchanger

Обоснована актуальность проведения исследований теплового состояния полой детали при нанесении металлических покрытий на поверхность отверстий методом термического испарения материала в вакууме с соосно расположенного стержневого резистивного испарителя. Проанализированы тепловые процессы, протекающие при вакуумном хромировании полых деталей, приведена схема теплообмена и составлено уравнение, описывающее тепловое состояние q ( t ) детали во время осаждения покрытия: . На покрываемую поверхность детали действуют тепловые потоки, образованные за счет излучения испарителя - плотностью q изл и выделения теплоты конденсации материала покрытия - плотностью q конд . Теплообмен между наружной цилиндрической поверхностью детали и внутренними устройствами вакуумной камеры характеризуется потоком плотностью qдет.нар; передача тепла от торцовых поверхностей детали к элементам технологической оснастки - потоком плотностью q тор . На эндотермическую реакцию фазового превращения в материале детали расходуется тепловой поток плотностью q фаз . Вследствие близкого расположения испарителя к покрываемой поверхности достаточно интенсивных режимов нанесения покрытий и хорошей теплоизоляции детали от элементов технологической оснастки принято, что тепло распространяется только в радиальном направлении; испарение материала происходит равномерно по всей длине испарителя; перераспределением тепла вдоль детали и тепловыми потерями ее торцов q тор пренебрегаем. Влияние теплоты эндотермической реакции фазового перехода q фаз решено не учитывать, поскольку формирование покрытия производят обычно при температурах, не превышающих температуру фазовых превращений в материале детали. С учетом описанных особенностей условий формирования покрытия составлено уравнение теплопроводности, определены начальные и граничные условия, разработана математическая модель теплового состояния основы (поверхности конденсации). Результаты теоретических исследований получены методом конечных разностей при использовании метода прогонки. Вычисления выполнены в соответствии с разработанным алгоритмом по программе расчета изменения температуры детали при формировании хромового покрытия на поверхности отверстий. Отличие расчетных данных математической модели от результатов экспериментальных исследований не превышает 5 %, что подтверждает достоверность полученной математической модели теплового состояния основы в процессе вакуумного хромирования полых деталей с использованием резистивного стержневого испарителя.

Experimental and computational study of melting phase-change material for energy storage in shell and tube heat exchanger

Evaluating the passive and free cooling application methods of phase change materials in residential buildings: A comparative study