scholarly journals Proposal for a solar fruit dryer design with organoleptic properties recovery system

2019 ◽  
Vol 80 ◽  
pp. 02003 ◽  
Author(s):  
D. Asmat-Campos ◽  
Angel Carreño-Ortega
Keyword(s):  
Heat Transfer ◽  
Fossil Fuels ◽  
Production Costs ◽  
Heat Transfer Fluid ◽  
Organoleptic Properties ◽  
Innovative Design ◽  
Quality Product ◽  
Recovery System ◽  
Organic Products ◽  
Trombe Wall

With the passing of time, the demand for dehydrated organic products has increased, ranging from vegetables to fruits, however in the latter efforts to achieve a quality product have led to the use of industrialized systems which depend on the use of fossil fuels or systems that use electric current which greatly increase production costs. At present, various solar dryer models have emerged, having achieved an optimal performance in what corresponds to the processing of vegetables, however in the processes of dehydration of fruits the results have not been satisfactory, due to the loss of its color, taste, aroma and texture (organoleptic properties). Faced with this problem, an innovative design of solar fruit dehydrator is proposed, which has two objectives, the first related to recovering the organoleptic properties through a system of condenzation, cyclic dehydration and the synchronization of the calorific balance, and the second one focused on the improvement of thermal efficiency, through the use of some heat piles and a trombe wall. The heat transfer fluid was improved, adding silver nanoparticles (silver nanospheres), which were synthesized using the green chemistry method; the efficiency of the heat transfer fluid was increased by 30%.

scholarly journals Performance Assessment of a Heat Recovery System for Monolithic Receiver-Reactors

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Stefan Brendelberger ◽  
Philipp Holzemer-Zerhusen ◽  
Henrik von Storch ◽  
Christian Sattler
Keyword(s):  
Heat Transfer ◽  
Energy Demand ◽  
Heat Recovery ◽  
Heat Transfer Fluid ◽  
Storage Unit ◽  
Thermochemical Cycles ◽  
Temperature Swing ◽  
Recovery System ◽  
Heat Recovery System ◽  
Material Studies

The most advanced solar thermochemical cycles in terms of demonstrated reactor efficiencies are based on temperature swing operated receiver-reactors with open porous ceria foams as a redox material. The demonstrated efficiencies are encouraging but especially for cycles based on ceria as the redox material, studies have pointed out the importance of high solid heat recovery rates to reach competitive process efficiencies. Different concepts for solid heat recovery have been proposed mainly for other types of reactors, and demonstration campaigns have shown first advances. Still, solid heat recovery remains an unsolved challenge. In this study, chances and limitations for solid heat recovery using a thermal storage unit with gas as heat transfer fluid are assessed. A numerical model for the reactor is presented and used to analyze the performance of a storage unit coupled to the reactor. The results show that such a concept could decrease the solar energy demand by up to 40% and should be further investigated.

Effects of Multi-Walled Carbon Nanotubes on Enhancing the Thermodynamics Characteristic of Alkali Nitrate and Chlorate Salt for Concentration Solar Plants

2013 ◽  
Vol 805-806 ◽  
pp. 63-69 ◽  
Author(s):  
Di Wu ◽  
Shi Liu
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Molten Salt ◽  
Fossil Fuels ◽  
Thermal Power ◽  
Thermal Storage ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Solar Thermal Power ◽  
The Future

Solar thermal power generation technology is the most feasible technology to compete with fossil fuels in the economy, and is considered to be one of the most promising candidates for providing a major share of the clean and renewable energy needed in the future. The appropriate heat transfer fluid and storage medium is a key technological issue for the future success of solar thermal technologies. Molten salt is one of the best heat transfer and thermal storage fluid for both parabolic trough and tower solar thermal power system. It is very important that molten salt heat transfer mechanisms are understood and can be predicted with accuracy. But studies on molten salts heat transfer are rare. This study will lay a foundation for the application of carbon nanotubes in molten salt which can remarkably improve the stability and capacity of thermal storage. Thermal analysis methods and scanning electron microscope (SEM) are utilized to provide a review of thermophysical properties and thermochemical characteristics of the MWCNTs-salt composite materials.

Experimental Studies of Natural Convection in Partitioned Enclosures With a Trombe Wall Geometry

1995 ◽  
Vol 117 (1) ◽  
pp. 16-21 ◽  
Author(s):  
R. O. Warrington ◽  
T. A. Ameel
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Experimental Studies ◽  
Heat Transfer Fluid ◽  
Test Facility ◽  
Fluid Temperature ◽  
Nusselt Numbers ◽  
Trombe Wall ◽  
Passive Solar ◽  
Wall Geometry

Natural convection heat transfer was investigated in a scaled test facility of a Trombe wall geometry. A silicone oil was employed as the convecting medium to obtain large Rayleigh numbers (up to 1.5 × 1010, based on enclosure height) characteristic of full-scale Trombe wall in a passive solar building. The main objectives were to study effects of Trombe wall nonisothermality and location on heat transfer, fluid temperature and fluid flow patterns. As expected, Nusselt numbers were slightly larger on the Trombe wall space side than on the living space side. Nusselt numbers increased slightly as the mass transfer gaps in the Trombe wall were increased. The results were verified, for the zero gap case, by comparing with previous studies. Physical understanding of the convection process was enhanced by flow visualization data. The information obtained should be useful to designers in optimizing overall building performance for passive solar heating.

Experimental Study on Thermal Characteristics of Finned Coil LHSU Using Paraffin as Phase Change Material

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Guansheng Chen ◽  
Nanshuo Li ◽  
Huanhuan Xiang ◽  
Fan Li
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Phase Change ◽  
Phase Change Material ◽  
Water Flow ◽  
Water Flow Rate ◽  
Thermal Characteristics ◽  
Heat Transfer Fluid ◽  
Latent Heat Storage ◽  
Change Material

It is well known that attaching fins on the tubes surfaces can enhance the heat transfer into and out from the phase change materials (PCMs). This paper presents the results of an experimental study on the thermal characteristics of finned coil latent heat storage unit (LHSU) using paraffin as the phase change material (PCM). The paraffin LHSU is a rectangular cube consists of continuous horizontal multibended tubes attached vertical fins at the pitches of 2.5, 5.0, and 7.5 mm that creates the heat transfer surface. The shell side along with the space around the tubes and fins is filled with the material RT54 allocated to store energy of water, which flows inside the tubes as heat transfer fluid (HTF). The measurement is carried out under four different water flow rates: 1.01, 1.30, 1.50, and 1.70 L/min in the charging and discharging process, respectively. The temperature of paraffin and water, charging and discharging wattage, and heat transfer coefficient are plotted in relation to the working time and water flow rate.

scholarly journals Numerical Evaluation of a HVAC System Based on a High-Performance Heat Transfer Fluid

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3298
Author(s):  
Gianpiero Colangelo ◽  
Brenda Raho ◽  
Marco Milanese ◽  
Arturo de Risi
Keyword(s):  
Heat Transfer ◽  
High Performance ◽  
Cooling System ◽  
Electrical Energy ◽  
Simulation Software ◽  
Heat Transfer Fluid ◽  
Hvac System ◽  
Dynamic Simulations ◽  
Heating And Cooling ◽  
The University

Nanofluids have great potential to improve the heat transfer properties of liquids, as demonstrated by recent studies. This paper presents a novel idea of utilizing nanofluid. It analyzes the performance of a HVAC (Heating Ventilation Air Conditioning) system using a high-performance heat transfer fluid (water-glycol nanofluid with nanoparticles of Al2O3), in the university campus of Lecce, Italy. The work describes the dynamic model of the building and its heating and cooling system, realized through the simulation software TRNSYS 17. The use of heat transfer fluid inseminated by nanoparticles in a real HVAC system is an innovative application that is difficult to find in the scientific literature so far. This work focuses on comparing the efficiency of the system working with a traditional water-glycol mixture with the same system that uses Al2O3-nanofluid. The results obtained by means of the dynamic simulations have confirmed what theoretically assumed, indicating the working conditions of the HVAC system that lead to lower operating costs and higher COP and EER, guaranteeing the optimal conditions of thermo-hygrometric comfort inside the building. Finally, the results showed that the use of a nanofluid based on water-glycol mixture and alumina increases the efficiency about 10% and at the same time reduces the electrical energy consumption of the HVAC system.

scholarly journals Modification of a Solar Thermal Collector to Promote Heat Transfer inside an Evacuated Tube Solar Thermal Absorber

2021 ◽  
Vol 11 (9) ◽  
pp. 4100
Author(s):  
Rasa Supankanok ◽  
Sukanpirom Sriwong ◽  
Phisan Ponpo ◽  
Wei Wu ◽  
Walairat Chandra-ambhorn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Small Scale ◽  
Medium Temperature ◽  
Change Behavior ◽  
Set Up ◽  
Evacuated Tube ◽  
Heating Medium

Evacuated-tube solar collector (ETSC) is developed to achieve high heating medium temperature. Heat transfer fluid contained inside a copper heat pipe directly affects the heating medium temperature. A 10 mol% of ethylene-glycol in water is the heat transfer fluid in this system. The purpose of this study is to modify inner structure of the evacuated tube for promoting heat transfer through aluminum fin to the copper heat pipe by inserting stainless-steel scrubbers in the evacuated tube to increase heat conduction surface area. The experiment is set up to measure the temperature of heat transfer fluid at a heat pipe tip which is a heat exchange area between heat transfer fluid and heating medium. The vapor/ liquid equilibrium (VLE) theory is applied to investigate phase change behavior of the heat transfer fluid. Mathematical model validated with 6 experimental results is set up to investigate the performance of ETSC system and evaluate the feasibility of applying the modified ETSC in small-scale industries. The results indicate that the average temperature of heat transfer fluid in a modified tube increased to 160.32 °C which is higher than a standard tube by approximately 22 °C leading to the increase in its efficiency by 34.96%.

scholarly journals Numerical Simulation of the Impact of the Heat Source Position on Melting of a Nano-Enhanced Phase Change Material

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1425
Author(s):  
Tarek Bouzennada ◽  
Farid Mechighel ◽  
Kaouther Ghachem ◽  
Lioua Kolsi
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Phase Change Material ◽  
Numerical Study ◽  
Melting Rate ◽  
Heat Transfer Fluid ◽  
Commercial Code ◽  
Tube Position ◽  
The Impact ◽  
Change Material

A 2D-symmetric numerical study of a new design of Nano-Enhanced Phase change material (NEPCM)-filled enclosure is presented in this paper. The enclosure is equipped with an inner tube allowing the circulation of the heat transfer fluid (HTF); n-Octadecane is chosen as phase change material (PCM). Comsol-Multiphysics commercial code was used to solve the governing equations. This study has been performed to examine the heat distribution and melting rate under the influence of the inner-tube position and the concentration of the nanoparticles dispersed in the PCM. The inner tube was located at three different vertical positions and the nanoparticle concentration was varied from 0 to 0.06. The results revealed that both heat transfer/melting rates are improved when the inner tube is located at the bottom region of the enclosure and by increasing the concentration of the nanoparticles. The addition of the nanoparticles enhances the heat transfer due to the considerable increase in conductivity. On the other hand, by placing the tube in the bottom area of the enclosure, the liquid PCM gets a wider space, allowing the intensification of the natural convection.

Experimental studies on micro-channel heat sink with different heat transfer fluid

2021 ◽  
Author(s):  
M. P. Dhanishk ◽  
P. Selvakumar ◽  
V. Ashwin ◽  
P. N. ArunKumar
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Experimental Studies ◽  
Heat Transfer Fluid ◽  
Micro Channel
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