ABSTRACT The aim of this study is to estimate the thermal diffusivity of metallic materials, in particular AISI 304 and AISI 316 stainless steel. To this end, an experimental setup based on the Angstrom’s method is used, where one face of a considerably large sample is subjected to a periodic heat flux and the other face is kept at a constant temperature. A low cost measurement system was developed

ABSTRACT The intensity of delayed fluorescence and kinetics processes of eosin molecules in a hanging drop of water solution with ablative silver nanoparticles and without them during phase change have been investigated in this work. Basing on the fluorescence data the obtained times of the initial stage of water-ice phase transitions were amount to 0.04 s and 0.067 s in solutions with and without

ABSTRACT This paper presents the experimental analysis of partially condensed refrigerant R-32 in an adiabatic straight capillary tube. The capillary test section is tested for variation of the mass flow rate for different inlet conditions. The capillary tube test section is selected for a diameter of 1.12 mm, 1.27 mm, and 1.52 mm, and for length 1000 mm, 1500 mm, and 2000 mm. The capillary inlet pressures

ABSTRACT It is a coupling solution for optimizing the materials with good thermal conductivity and anti-corrosive modified coating of flue-gas condensation heat exchangers. The paper experimentally studied the condensation heat transfer between the wet air and 3-D finned-tube heat exchanger surface in three different ways, i.e. non-coating, Ni-Cu-P organic pure-coating, and Ni-Cu-P chemical organic

ABSTRACT The boiling heat-transfer performances of R1234ze(E)/R152a (0.4/0.6 by mass) flowing inside a horizontal micro-fin tube of 9.52 mm outer diameter were researched by experiment. Under the experimental conditions of mean vapor quality between 0.02 and 0.98 with the mass flux of 50 ~ 100 kg/(m2·s), saturation temperature from 12 to18°C and heat flux from 5 to 20 kW/m2, and the impacts of mass

ABSTRACT The pulse tube refrigerator is a closed cycle mechanical refrigerator with no mobile components working in a low-temperature area. The pulse tube refrigerator provides significant potential and has certain benefits viz., vibration-free, huge reliability, and economical for long span performance. In this paper, the experimental investigations performed on a single-stage Gifford-McMahon type

ABSTRACT The effects of input parameters such as pressure, mass flux, and inlet subcooling on bubble departure diameter, frequencies, and quadrupole magnetic field have been investigated. It was observed that process of changes in diameter and bubble departure frequency was similar with and without magnetic field, and the bubbles proved a regulated growth in the presence of a magnetic field. Compared

ABSTRACT This paper investigates the effect of the combined passive technique on heat transfer enhancement, friction factor, and thermal performance of a double-tube heat exchanger fitted with differently configured turbulators and using Alumina nanofluid. The performance parameters are studied for fixed flow rate (Re = 2500) of water at constant heat flux in the inner tube (hot fluid) and varying

ABSTRACT In this study, the temporal and spatial temperature distribution of the heat storage mortar made of porous feldspar was measured and the thermal properties and electricity consumption were analyzed. To compare the effects of porous feldspar mortar, two real-size models (control and test model) were constructed. The surface temperature change of the heat storage layer was remotely monitored

ABSTRACT This paper is focused on the effects of different evacuation pressures on thermal performance of vertically placed flat-plate pulsating heat pipe (FP-PHP). Experimental results show that the difference in the amount of non-condensable gas (NCG) caused by evacuation pressures is an important reason for the difference in thermal performance of FP-PHP. The water FP-PHP under evacuation pressure

ABSTRACT The thermal performance of a flat-plate solar collector (FPSC) using novel heat transfer fluids of aqueous colloidal dispersions of covalently functionalized multi-walled carbon nanotubes with β-Alanine (Ala-MWCNTs) has been studied. Multi-walled carbon nanotubes (MWCNTs) with outside diameters of (< 8 nm) and (20–30 nm) having specific surface areas (SSAs) of (500 m2/g) and (110 m2/g), respectively

ABSTRACT The present article is focused to improve the thermal performance of solar air heater using Liquid crystal thermography (LCT) approach, an improved type solar air heater comprises of winglet type rib roughened surface. In the present case, an experimental analysis and its effects on heat transfer and collector efficiency are examined using non-dimensional roughness parameters taken as relative

ABSTRACT In this paper, the effect of various zinc oxide aluminate spinel (ZnOAl2O3) and titanium oxide (TiO2) nanoparticle concentrations on the thermal performance of the Diffusion Absorption Refrigeration (DAR) system is investigated. The main aim of the study is to increase the efficiency of DAR systems operating with low thermal performance. The first part of the study is experimentally tested

ABSTRACT We report the development of transparent high-thermal-conductivity nanofluids for enhanced flow cooling of solid-state laser crystal rods. The transparent nanofluids were prepared by dispersing citrate-stabilized Au nanoparticles in water and strictly controlling the particle size and loading. The Au nanofluids have shown stable dispersion, high optical transparency at the excitation wavelength

ABSTRACT Many troubles appear when vehicles work in the plateau region, and the main reason is that the heat-transfer capability of radiator in the vehicle cooling system reduces under the plateau low air pressure environment. Hence, the research on the flow and heat transfer characteristics of radiators in plateau low air pressure environment is necessary. In this paper, the experimental study on

ABSTRACT Present experimental study reports the thermal and flow measurement of multiple-orifice synthetic jet involving circular, square, and rectangular orifice shapes. Here, an infrared camera and constant temperature anemometer are used for measurement of surface temperature and flow velocity, respectively. Reynolds number and the dimensionless axial distance is varied within 1689–4670 and 1–25

ABSTRACT Three micro-finned and two smooth multiport tubes having the same tube width and height with the microfin tubes were tested using R-410A. For the smooth multiport tube, the tube with smaller hydraulic diameter yielded both higher heat transfer coefficients and larger pressure drops. However, for the microfin tube, results suggested that, fin configuration (number of fins per channel, fin height

ABSTRACT The thermohydraulic effect of microstructuring of the heat transfer surfaces of plate heat exchanger was studied experimentally. The aim of this enhancement strategy is to raise the heat transfer coefficient for the evaporation and condensation of the refrigerant in a vapor compression cycle up to the same level as typical single-phase heat transfer coefficients, when water is used as a secondary

R-134a distribution in an evaporator having two-row/six-pass configuration was experimentally studied with the inlet quality 0.2 and the outlet superheat 5°C. The mass flux was varied from 63 kg/m2s to 117 kg/m2s. The flow distribution generally followed the expected trend. The insert configuration (multi-hole or a single rectangular hole) affected only nearly passes. Furthermore, better liquid distribution

The assembly step between the vane and blade in a gas turbine exists because of the rotating blade and expansion of the external flow passage. The assembly step has a great impact on the heat transfer distribution on the endwall. In this study, a rod was installed in front of the blade to generate non-uniform inlet flow and to observe the heat transfer characteristics on the endwall. The mass transfer

Rates of mass and heat transfer (by analogy) at the surface of a helical coil imbedded in a fixed bed of inert cylindrical packing were measured under upward two-phase (gas-liquid) flow by the electrochemical technique. The effects of geometrical and hydrodynamic parameters were considered. The performance of cylindrical packing was compared with that of Raschig rings and spheres. The analogy between

Thermal energy storage system has significant influence on energy conservation. Based on the literature review, it is identified that very few studies have been reported on performance assessment of latent and sensible thermal energy storage systems. This study presents an experimental study on latent and sensible thermal energy storage systems to investigate their performance during discharging cycle

Turbulators have been developed as a capable passive technique for enhancing heat transfer through channels. The shape and arrangement of these geometries are the main factors in their performance. In the current analysis, three curved turbulators, i.e. circular (C), rectangular (R), and diamond (D), with four various arrangements, i.e. forward-vertical (FV), forward-horizontal (FH), backward-vertical

The condensation heat transfer characteristics of a new environmental refrigerant mixture R1234ze (E)/R152a (mass ratio 40:60, named NCUR01) in a horizontal micro-fin tube with an outer diameter of 9.52 mm were experimentally investigated. Experiments were conducted at saturation temperatures of 30°C, 35°C and 40°C, heat flux ranged from 3 to 8 kW·m−2, mass flux ranged from 25 to 75 kg·m−2·s−1, and

In the context of emission-free electricity generation, the authors developed a novel hydrogen-oxygen combustor, which is based on swirl-stabilized combustion technology and steam dilution. Following previous burner characterization, the current study investigates the heat transfer conditions in the combustion chamber wall. To this end, a carefully controlled co-flow of air is used to cool the combustion

Jet impingement on absorber plate with hemispherical protrusion is taken up for heat and friction characteristics analysis, where the protrusions are provided exactly below the jet holes to provide impingement over the protrusions for generating larger turbulence. The geometric parameters selected for experimental analysis are Relative protrusion diameter to protrusion height ratio ( d p r / e p r

Experiments have been conducted on a flat rectangular loop heat pipe with water and methanol at heat loads from 40 to 320 W at three orientations of the heat pipe (0°, 45°, 90°) and two filling ratios (33% and 50%). Performance parameters such as thermal resistance, effective thermal conductivity and capillary limit are calculated from the experimental data. The results exhibited that the thermal performance

Low-pressure refrigerants such as R245fa allow compact design of IT cooling systems intended for harsh environments. Nucleate boiling of R245fa on an electrically heated flat horizontal surface was experimentally studied. Heat fluxes q w were 30–65 k W / m 2 and saturation temperatures 40–70   ∘ C. Results show that the heat-transfer coefficient HTC increases with both heat flux and temperature, and

Steady-state experiments are conducted under the laminar forced convection heat transfer mode for the cooling of seven asymmetric IC chips (heat sources) mounted at different positions on the substrate board. The board is oriented at different angles, i.e., at 0° (horizontal), 30°, 60°, and 90° (vertical) to study its effect on the cooling of the IC chips. The goal is to determine the optimum configuration

An experimental study on the antifouling performance of ultrasonic and/or electronic treatment was carried out in a convective heat transfer process by using a fouling monitor system. An ultrasonic device was used in a frequency of 28 kHz and a power of 80 W, and a low-voltage electronic processor also used with a maximum current of 0.8 A for water treatment. The experimental results showed that both

This work aims to estimate the experimental heat transfer coefficients of a circular channel using artificial neural network. The experiments are carried out at a forced turbulent flow regime of 10,000 < Re <50,000. The obtained experimental Nusselt numbers are compared using the ANN (Artificial Neural Network). In the developed ANN structure are showed mean square error (MSE), average relative deviation

The purpose of this experimental study is to measure the drag and heat transfer coefficients of the non-circular tubes including square, elliptic, and cam-shape tubes in a turbulent air cross flow. Studies have been made at 0° to 180° angles of attack ( α ) and Reynolds numbers (Re) based on the equivalent diameter of a circular tube within the range of 1.4 × 104 < Reeq < 7.5 × 104. The equivalent

An experimental study has been performed to analyze the heat transfer characteristics by impinging a hybrid nanofluid jet on horizontal-heated test surface. The Ag/ZnO nanoparticles are synthesized and dispersed in DI water Φ = 0.02% to 0.1% by volume. A set of experiments were performed to calculate heat transfer coefficient and boiling performance at varying Reynolds numbers ranging from 1769 to

The current paper is focused on the experimental investigation of the turbulent forced convection with circular-hole spring tape (CHST) inserts in a circular tube. The CHST inserts with different hole and spring ratios, are investigated for a wide ranges of Reynolds number (10,000–50,000). Results show that use of CHST provides an increase in heat transfer by 35% and 51% when assessed with other inserts

It is hypothesized that the heat transfer in microgravity bubbly flow boiling can be computed through a single-flow simulation that accounts for the acceleration of the liquid as bubbles form since the slip velocity in microgravity is negligible. Measurements within the bubbly flow regime were obtained in a 6 mm ID sapphire tube in microgravity using HFE-7000 at four mass fluxes, six heat fluxes, and

Effect of upward two-phase gas-liquid flow on the rate of liquid-solid mass transfer in a bubble column equipped with a horizontal tube bundle was studied by measuring the rate of the diffusion-controlled dissolution of copper in an acidified K2Cr2O solution. Variables studied included gas (nitrogen) flow rate, liquid flow rate, and the number of tube arrays. Data were successfully correlated by a

Impact of using V-cuts twisted tape insert and phase change material (PCM) dispersed mono or hybrid nanofluid on the hydrothermal characteristics of the double tube heat exchanger is experimentally investigated. Water-based Al2O3 and PCM nanofluids and Al2O3+ PCM hybrid nanofluid with different concentrations are used in inner tube. Influences of various geometric parameters of V-cuts twisted tape

In this experimental investigation, the impact of engine load, compression ratio, and percentage blends of biofuel on exergy, energy, and sustainability parameters for the samples of diesel based (10–40% v/v) biodiesel blends were performed on variable compression ratio engine. The brake thermal efficiency, exergy efficiency, engine sustainability, exergy destruction rate, and other exergy parameters

A version improving the efficiency of the Trombe-type assembly is proposed in this study. It consists in equipping the wall with a series of inclined fins forming open cavities of parallelogram section affecting the aerodynamics of the active cavity. The natural convective flow leads to an increase in natural convective heat transfer and improves the overall performance of the assembly. The experimental

Critical Heat Flux (CHF) is one of the catastrophic failure modes encountered in two-phase flows in nuclear, chemical, and power industries. Considerable research was carried on CHF in last few decades in horizontal, inclined, and vertically upward flows. Only limited information, mostly at atmospheric pressure conditions and including CHF enhancers like inlet throttling, was available on CHF in vertical

The present study aims to investigate the effects of the pin on flow and heat transfer from pulsating jet impinging on a heated flat surface. A row of cylindrical pins has been applied on a flat plate with a constant heat flux of 2000 W/m2. The experiments have been performed for two jet to target surface distances, frequency range from 50 Hz to 100 Hz and jet Reynolds number from 7000 to 15000. The

The K, E, and J-types of coaxial thermocouples have been designed and fabricate to perform transient heat flux evaluation at the combustion chamber of a four-stroke diesel engine. These coaxial thermocouples are quite efficient in short-duration transient measurements due to the response time of these instruments are in the rage of milliseconds or less. Using water plunging technique, the thermal product

In the present study, an experimental investigation of performance evaluation of plate heat exchanger (PHE) with the rough surface using AL2O3/water nanofluid was achieved. The experiments were developed for different surface roughnesses of 0.978 µm (smooth surface), 1.276 µm, 2.825 µm and 3.657 µm with different volume fractions of nanoparticles of 1.2 vol.%, 1.9 vol.% and 2.6 vol.% at Reynolds number

Mixed convective heat transfer from horizontal isothermal elliptic cylinder is experimentally studied. Three elliptic test cylinders with same perimeter and length are studied giving axis ratio (AR) equal 1, 0.709 and 0.496. The corresponding Gr for the three test sections is 9.8 × 105, 1.5 × 106, and 2.1 × 106, and Re varies from 111 to 1306. Consequently, the corresponding Ri is in range of 1 to

Experimental results of natural convection in an open-ended concentric and eccentric annulus with helical fin on internal tube are presented. The boundary condition investigated is constant temperature for the inner tube while the outer tube is insulated. The effect of pitches and fin diameter under several different constant temperatures applied on the inner tube at concentric and different eccentric

An experimental study of average heat transfer from air jet impinging on a rough plate by a micro cubic pin is investigated. The main objective of the present study is to investigate the effect of a roughened degree on both local and average Nusselt number. The micro cubic size is (400 µm × 400 µm) with different depths (100, 200, and 300 µm). Therefore, the roughened degree varies between 1.0 (considered

We presented both experimental and numerical studies on the freezing of impacting water droplets on a cold surface at different surface temperatures. The numerical model consists of two parts. The first one is to determine the temperature evolution of the droplet prior to the occurrence of freezing by solving the heat conduction equation, and the second one is to simulate the freezing process via an

In this experimental study, the effect of natural convection during the melting and solidification process on nano-enhanced phase change material in a designed cylindrical thermal energy storage system has been investigated. The temperature variations at both axial and radial locations are measured for stearic acid PCM with variation in mass fractions (0.1%, 0.3%, and 0.5%) of Al2O3 nano-additives

ABSTRACT Studies have previously looked at the transport processes in convection but there is a lack of detail on methods to characterize transient heat transfer behavior. An infrared methodology to spatially and temporally resolve transient heat transfer is presented and tested on turbulent impinging (cooling) jets (non-swirling, swirling, Re = 11,600 to 35,000, S = 0 to 1.05). The intricacies of

The near-azeotropic refrigerant mixture R1234ze(E)/R152a (40/60 by mass%) was an excellent alternative refrigerant with outstanding environmental protection and thermophysical properties as well as good cycle performance. The flow boiling heat transfer characteristics of R1234ze(E)/R152a (40/60 by mass%) in horizontal smooth copper tube with inner diameter (ID) of 6 mm were investigated experimentally

Pool boiling is the process in which the heating surface is submerged in a large body of stagnant liquid. In the present work, heat transfer in nucleate pool boiling is modeled both experimentally and semi-analytically with the consideration of surface structuring methods including wire electrical discharge machining (WEDM) and etching. The developed models consider variations of nucleation site density

The cross flow over the tube bank is extensively employed in the heat exchangers. The present study investigates the heat transfer and frictional losses of cross flow tube bank with solid and perforated splitter plates. The experimental data are collected for bare tube bank, tube bank with solid and perforated splitter plate by varying the splitter plate width ratio (Rw) and the perforation index (Pi)

ABSTRACT A dual-wavelength Mach–Zehnder interferometer technique is used for the investigation of thermodiffusion through 5 mass% NaCl solution at temperature differences of 3°C, 5°C, and 8°C applied across the cavity. Initially, the values of thermal diffusivity and thermodiffusion coefficients are measured from the highly sensitive data of temperature and concentration distribution through sensitivity

ABSTRACT Saline soils is porous medium whose thermal conductivity is affected by components and particle shape. However, the particle shapes in geomaterials are various, and the component and its content are in dynamic change as the soil varies between unfrozen and frozen state. In this study, based on the theory of multi-phase medium mixed geothermal conductivity, a new model is developed to explore

Previous researches mainly focused on the cooling performance of the vortex tube. Here, the heating performance indicators such as hot temperature difference, heating rate per unit air, and coefficient of performance are investigated experimentally. The results show that the maximum heating separation is obtained when the cold mass fraction is in the range of 0.45–0.7. The influence of inlet pressure

ABSTRACT Rates of mass transfer in a spiral coil were measured by a technique involving the diffusion-controlled dissolution of copper in acidified dichromate. The variables studied were solution velocity, spiral tube pitch, and physical properties of the solution. The data were correlated by the equation Sh=0.189Sc0.33De0.55Pd0.29 For a given set of conditions, the mass transfer coefficient predicted

ABSTRACT The current study presents the energy and exergy analysis of a thermoelectric waste heat recovery system of an automobile using an aluminum-based heat exchanger. The experiment was conducted on a 4 cylinder direct injection diesel engine by varying the load with constant engine speed. Effect of second law efficiency, availability, entropy generation along with output current, and power of

ABSTRACT Flow boiling experiments were conducted in a staggered array micro pin fin channel heat sink with deionized water for two-phase pressure drop and boiling heat transfer at constant heat flux. Micro pin fin is a diameter of 400 μm, height of 700 μm and spacing of 300 μm on copper heat sink. From the experimental results, at a vapor quality up to 0.043, the boiling heat transfer found to decrease

ABSTRACT Thermal characteristics of water in a ground U-tube with twisted tape inserts were addressed. At inlet temperatures of 60°C to 75°C, and Reynolds numbers of 3000 to 9000, the surface heat transfer coefficients for water with twisted tapes ranged from 442 to 897 W m−2 K−1, which were higher than that in smooth tube, 384–810 W m−2 K−1. Average convective heat transfer coefficient for the smooth

ABSTRACT The studies of nested helical coil heat exchangers for an absorption heat transformer are very limited, although this arrangement has a greater heat transfer area in a smaller volume. The heat exchangers are vertically placed to develop the desorption, condensation, evaporation and absorption processes by falling film mode. The usage of energy from point of qualitative view in these times