Solar Engineering Of Thermal Processes

An investigation on solar drying: A review with economic and environmental assessment

Effect of air recirculation and heat pump on mass transfer and energy parameters in drying of kiwifruit slices

Drying and dynamic performance of well-adapted solar assisted heat pump drying system

Solar assisted heat pump (SAHP) system integrates a solar thermal energy source with a heat pump. This technique is a very fundamental concept, especially for drying applications. By combining a solar thermal energy source such as solar thermal collectors and a heat pump dryer will assist in reducing the operation cost of drying and producing products with high quality. Many review papers in the literature evaluated the R&D aspects of solar-assisted heat pump dryers (SAHPD). This critical review paper studies some of the researches conducted in this field to understand and provides an update on recent developments in SAHPD. Also, a detailed explanation of principles and operation for SAHPD and its applications are presented. The used types of solar thermal collectors, as well as various heat pump dryers, are all discussed in this article. Finally, it is concluded that there is clear lack of research in the techno-economic and environmental evaluati0on, while most of SAHPD studies focused on the performance study of the system.

https://www.ijrer.com/index.php/ijrer/article/download/10403/pdf

Solar Assisted Heat Pump System for High Quality Drying Applications: A Critical Review

In this investigation, dissimilar welded joints of AISI 316 L and AISI 310S stainless steels were produced using continuous and pulsed modes current of the gas tungsten arc welding process. A filler metal type ER309L was used to strengthen the welded joints. The fracture mode of the tensile and Charpy impact test samples was studied using a field emission scanning electron microscope (FE-SEM). Results showed that the welded joints were broken in the 316 L steel side during the tensile test due to the presence of lower alloying elements in this steel compared with the AISI 310S stainless steel. As well, microhardness and Charpy impact tests results showed that changing the welding current from continuous to the pulsed one increased the values of these two mentioned attributes. Fractography analysis, performed on the fracture surfaces of both joints, showed a completely ductile fracture under both tensile and Charpy impact tests. Moreover, microstructural observations showed that the weld metal (WM) structure was austenitic-ferritic (AF) and contained columnar and equiaxed dendrites. Changing the welding current from the continuous to the pulsed one led to the transformation of the columnar dendrites to the very fine equiaxed dendrites. This welding current variation reduced the dendrite size of the WM and decreased the area of the unmixed zone (UMZ). Finally, XRD results indicated that austenite was the predominant phase in the welded joints. 

Experimental investigation on the effect of gas tungsten arc welding current modes upon the microstructure, mechanical, and fractography properties of welded joints of two grades of AISI 316L and AISI310S alloy metal sheets

In this study, a solar dryer assisted with heat pump was developed and thin layer drying of dill was carried out at air temperatures of 40, 50, and 60oC and air velocities of 0.5, 1 and 1.5 ms. Also, the drying rates, Specific Moisture Extraction Rate (SMER), and energy consumption were evaluated. Dill samples were dried from initial moisture content of 90% to the final moisture content of 10% in 195-275 minutes without assisted heat pump, and with assisted heat pump in 80-140 minutes. By using heat pump, the drying rate increased with increase in temperature at a given air velocity, thus, reducing the drying time. Increase in the air velocity at a given temperature improved the drying rate. By increasing the air velocity from 0.5 to 1.5 m s, drying time decreased up to 42%. The specific moisture extraction rate values were found to vary between 0.078 and 0.18 Kg Kw h. The minimum value of energy consumption was 3312 kJ at air temperature of 60oC and air velocity of 1.5 m s. Also, the total energy consumption of dryer with heat pump was reduced by 19%, which reflects the higher energy efficiency.

Experimental Investigation on Dill Drying in a Solar-Assisted Heat Pump Dryer

The effect of high-pressure torsion (HPT) on textural components and microstructural evolution of an Fe–10Ni–7Mn steel was investigated. Six turns of HPT, with a rotation rate of 1 rpm and with a pressure of 6.0 GPa, were applied to a solution annealed steel. Microstructural and textural evolution, including dislocation characteristics and grain size/misorientation measurements, were accomplished using electron backscatter diffraction (EBSD). The results showed that a fully martensitic structure, containing a high density of dislocations, was developed during the solution annealing stage and subsequently the application of six turns of HPT process converted the low-angle grain boundaries (LAGBs) of the solution annealed condition into high-angle grain boundaries (HAGBs). Thus, the sub-grain boundaries established in the solution annealed condition were altered into very sharp HAGBs. The grain size was also decreased from ∼ 25 μm in the solution annealed situation to ∼210 nm in the severely deformed condition of six-turn high-pressure torsion state. Yield strength, and tensile strength were increased from 765 MPa, and 840 MPa in the solution annealed case to 1890 MPa, and 2230 MPa in the six-turn HPT-processed sample, respectively. Under such a condition, ductility was decreased from 15.2% to 6.1% in the severely deformed state. Applying six turns of HPT developed a predominantly {111}//ND texture. However, the overall texture intensity of the HPT-processed sample was weakened to a value of about one-quarter of the as-quenched solution treated sample. This was related to dynamic recrystallization and grain subdivision as well as a dislocation density reduction in the HPT-processed sample. The texture components of strong Copper ({112}<111>), S ({123}<634>) and some average intensity Cube {100}<0001> were observed in the {100} pole figure in the solution annealed condition. As well, γ-fibre (<111>//ND) and β-fibre were seen in this condition. However, {110}<uvw> fibres were mostly developed in the six-turn sample with the texture components of E1{011‾}<111>, E2{01‾1}<111>, J1{01‾1}<2‾11>, J2+{11‾0}<1‾1‾2>, D2{1‾1‾2}<111> , D1{112‾}<111> and F {110}<001>. In addition, the Cu{112}⟨111⟩ component was significantly diminished. This weakened Cu{112}⟨111⟩ component would have caused enhancement of the mechanical properties, particularly the formability and toughness, as previously reported by the current authors. Finally, it was found that applying severe plastic deformation (SPD) in the form of HPT reduces the effect of martensitic texture in the solution treated steel. 

Evaluation of texture weakening and microstructural evolution in an Fe–10Ni–7Mn martensitic steel severely deformed by six turns of high-pressure torsion

H. Jafarian

Papers

Experimental investigation on the effect of gas tungsten arc welding current modes upon the microstructure, mechanical, and fractography properties of welded joints of two grades of AISI 316L and AISI310S alloy metal sheets

Experimental Investigation on Dill Drying in a Solar-Assisted Heat Pump Dryer

Evaluation of texture weakening and microstructural evolution in an Fe–10Ni–7Mn martensitic steel severely deformed by six turns of high-pressure torsion

Finite Element Simulation and Experimental Investigation of Hot Forming Cold Die Quenching and Equal Channel Angular Pressing of AA2024 Aluminum Alloy