Experimental investigations on jet impingement solar air collectors using pin-fin absorber

2020 ◽  
pp. 095440892093530 ◽  
Author(s):  
C Kannan ◽  
M Mohanraj ◽  
P Sathyabalan
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Jet Impingement ◽  
Climatic Conditions ◽  
Solar Irradiation ◽  
Experimental Investigations ◽  
Air Mass ◽  
Pin Fin

In this paper, the performances of a novel jet impingement solar air collector (JISAC) using flat and pin-fin absorbers were experimentally investigated. The experimental observations in a JISAC have been made under the climatic conditions of Coimbatore city in India during the year 2019. The thermo-hydraulic analyses were conduced to study the influence of pressure drop across the perforated jet plate. The effects of solar irradiation, ambient temperature, ambient wind velocity and air mass flow rate through the JISAC duct using flat and pin-fin absorbers were studied. The air mass flow rate through the JISAC was optimized to 0.025 kg/s based on the experimental trials. Thermodynamic performance comparisons have been made among the flat and pin-fin absorbers. The results showed that, the JISAC using pin-fin absorber has 2–7°C higher air temperature at the outlet with 3–7%, 2–6% and 2–6% improved energy efficiency, thermo-hydraulic efficiency and exergy efficiency, respectively when compared to the JISAC using flat absorber. The pressure drop across the JISAC duct is about 90% higher when compared to the conventional solar air collectors. The pressure drop through the jet plate has increased the air velocity impinging on the absorber. As a result, the heat transfer coefficient between air and the absorber has been significantly improved.

scholarly journals Experimental study of the pressure loss in aero-engine air-oil separators

2017 ◽  
Vol 121 (1242) ◽  
pp. 1147-1161 ◽  
Author(s):  
A. Laura Cordes ◽  
B. Tim Pychynski ◽  
C. Corina Schwitzke ◽  
D. Hans-Jörg Bauer ◽  
A. Thiago P. de Carvalho ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotational Speed ◽  
Pressure Loss ◽  
Metal Foam ◽  
Separation Efficiency ◽  
Air Mass ◽  
Aero Engine

ABSTRACTThe results of extensive experimental testing of an aero-engine air-oil separator are presented and discussed. The study focuses on the pressure loss of the system. Oil enters the device in the form of dispersed droplets. Subsequently, separation occurs by centrifuging larger droplets towards the outer walls and by film formation at the inner surface of a rotating porous material, namely an open-cell metal foam. The work described here is part of a study led jointly by the Karlsruhe Institute of Technology (KIT) and the University of Nottingham (UNott) within a recent EU project.The goal of the research is to increase the separation efficiency to mitigate oil consumption and emissions, while keeping the pressure loss as low as possible. The aim is to determine the influencing factors on pressure loss and separation efficiency. With this knowledge, a correlation can eventually be derived. Experiments were conducted for three different separator configurations, one without a metal foam and two with metal foams of different pore sizes. For each configuration, a variety of engine-like conditions of air mass flow rate, rotational speed and droplet size was investigated. The experimental results were used to validate and improve the numerical modelling.Results for the pressure drop and its dependencies on air mass flow rate and the rotational speed were analysed. It is shown that the swirling flow and the dissipation of angular momentum are the most important contributors to the pressure drop, besides the losses due to friction and dissipation caused by the flow passing the metal foam. It was found that the ratio of the rotor speed and the tangential velocity of the fluid is an important parameter to describe the influence of rotation on the pressure loss. Contrary to expectations, the pressure loss is not necessarily increased with a metal foam installed.

Heat Transfer, Pressure Drop, and Mass Flow Rate in Pin Fin Channels With Long and Short Trailing Edge Ejection Holes

1989 ◽  
Vol 111 (2) ◽  
pp. 116-123 ◽  
Author(s):  
S. C. Lau ◽  
J. C. Han ◽  
T. Batten
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Radial Flow ◽  
Trailing Edge ◽  
Test Channel ◽  
Pin Fin ◽  
Edge Flow

Experiments have been conducted to study the turbulent heat transfer and friction characteristics in pin fin channels with small trailing edge ejection holes that are commonly found in modern internally cooled turbine airfoils. The main objective of the investigation is to examine the effects of varying the length and the configuration of the trailing edge ejection holes on the overall heat transfer, the overall pressure drop, the local pressure distribution, and the local mass flow rate distribution in the pin fin channel. The staggered pin fin array (L/D = 1.0, X/D = S/D = 2.5) in the test channel has 15 rows of three pins. The diameter of the ejection holes is one-half the diameter of the pins. There are 30 or 23 ejection holes on one of the side walls of the test channel and six similar ejection holes at the radial flow exit. Experimental results are obtained for two trailing edge ejection hole lengths, four ejection hole configurations, and Reynolds numbers between 10,000 and 60,000. The results show that the overall heat transfer increases when the length of the trailing edge ejection holes is increased and when the trailing edge ejection holes are configured so that much of the cooling air is forced to flow farther downstream in the radial flow direction before exiting the pin fin channel through ejection holes. The overall Nusselt number can be correlated with an equation of the form NuD = a (ReD)b, where the values of the exponent b are about the same for all the test cases with trailing edge flow ejection. Results also show that the increase in the overall heat transfer is generally accompanied by an increase in the overall pressure drop (that is, an increase in the required pumping power), except that the overall heat transfer is lower and the overall pressure drop is higher when there is no radial flow ejection. In the cases with both radial and trailing edge flow ejection, about 15 to 20 percent of the flow exits through the tip bleed holes.

Research on Two-Phase Flow Instability in Evaporator of Refrigeration System

2010 ◽  
Author(s):  
Nan Liang ◽  
Changqing Tian ◽  
Shuangquan Shao
Keyword(s):  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Two Phase Flow ◽  
Density Wave ◽  
Phase Flow ◽  
Constant Mass ◽  
Refrigeration System ◽  
Two Phase

As one kind of fluid machinery related to the two-phase flow, the refrigeration system encounters more problems of instability. It is essential to ensure the stability of the refrigeration systems for the operation and efficiency. This paper presents the experimental investigation on the static and dynamic instability in an evaporator of refrigeration system. The static instability experiments showed that the oscillatory period and swing of the mixture-vapor transition point by observation with a camera through the transparent quartz glass tube at the outlet of the evaporator. The pressure drop versus mass flow rate curves of refrigerant two phase flow in the evaporator were obtained with a negative slope region in addition to two positive slope regions, thus making the flow rate a multi-valued function of the pressure drop. For dynamic instabilities in the evaporation process, three types of oscillations (density wave type, pressure drop type and thermal type) were observed at different mass flow rates and heat fluxes, which can be represented in the pressure drop versus mass flow rate curves. For the dynamic instabilities, density wave oscillations happen when the heat flux is high with the constant mass flow rate. Thermal oscillations happen when the heat flux is correspondingly low with constant mass flow rate. Though the refrigeration system do not have special tank, the accumulator and receiver provide enough compressible volume to induce the pressure drop oscillations. The representation and characteristic of each oscillation type were also analyzed in the paper.

Heat Transfer and Flow Friction Characteristics for Compact Cold Plates

2003 ◽  
Vol 125 (1) ◽  
pp. 104-113 ◽  
Author(s):  
Chang-Yuan Liu ◽  
Ying-Huei Hung
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Thermal Resistance ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Average Nusselt Number ◽  
Cold Plate ◽  
Air Mass

Both experimental and theoretical investigations on the heat transfer and flow friction characteristics of compact cold plates have been performed. From the results, the local and average temperature rises on the cold plate surface increase with increasing chip heat flux or decreasing air mass flow rate. Besides, the effect of chip heat flux on the thermal resistance of cold plate is insignificant; while the thermal resistance of cold plate decreases with increasing air mass flow rate. Three empirical correlations of thermal resistance in terms of air mass flow rate with a power of −0.228 are presented. As for average Nusselt number, the effect of chip heat flux on the average Nusselt number is insignificant; while the average Nusselt number of the cold plate increases with increasing Reynolds number. An empirical relationship between Nu¯cp and Re can be correlated. In the flow frictional aspect, the overall pressure drop of the cold plate increases with increasing air mass flow rate; while it is insignificantly affected by chip heat flux. An empirical correlation of the overall pressure drop in terms of air mass flow rate with a power of 1.265 is presented. Finally, both heat transfer performance factor “j” and pumping power factor “f” decrease with increasing Reynolds number in a power of 0.805; while they are independent of chip heat flux. The Colburn analogy can be adequately employed in the study.

scholarly journals Analytical and Experimental Investigation of a Plate Fin Heat Exchanger at Cryogenics Temperature

2021 ◽  
Vol 39 (4) ◽  
pp. 1225-1235
Author(s):  
Ajay K. Gupta ◽  
Manoj Kumar ◽  
Ranjit K. Sahoo ◽  
Sunil K. Sarangi
Keyword(s):  
Heat Exchanger ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cryogenic Temperature ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Compact Size

Plate-fin heat exchangers provide a broad range of applications in many cryogenic industries for liquefaction and separation of gasses because of their excellent technical advantages such as high effectiveness, compact size, etc. Correlations are available for the design of a plate-fin heat exchanger, but experimental investigations are few at cryogenic temperature. In the present study, a cryogenic heat exchanger test setup has been designed and fabricated to investigate the performance of plate-fin heat exchanger at cryogenic temperature. Major parameters (Colburn factor, Friction factor, etc.) that affect the performance of plate-fin heat exchangers are provided concisely. The effect of mass flow rate and inlet temperature on the effectiveness and pressure drop of the heat exchanger are investigated. It is observed that with an increase in mass flow rate effectiveness and pressure drop increases. The present setup emphasis the systematic procedure to perform the experiment based on cryogenic operating conditions and represent its uncertainties level.

scholarly journals Optimal design to control rotor shaft vibrations and thermal management on a supercritical CO2 microturbine

2021 ◽  
Vol 22 ◽  
pp. 22
Author(s):  
Jun Li ◽  
Hal Gurgenci ◽  
Jishun Li ◽  
Lun Li ◽  
Zhiqiang Guan ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Jet Impingement ◽  
Brayton Cycle ◽  
Cooling Device ◽  
Resonance Amplitude ◽  
Chaotic Mapping ◽  
The Given

Supercritical carbon dioxide (SCO2) Brayton cycle microturbine can be used for the next generation of solar power. In order to comprehensively optimize the supporting system and cooling device parameters of Brayton cycle shafting, the concept of chaos interval is introduced by chaotic mapping, and the CIMPSO algorithm is proposed to optimize the multi-objective rotor system model with nonlinear variables.The results show that the resonance amplitude of the optimized model is effectively attenuated, and the critical speed point is far away from the working speed, which shows the robustness of the optimization algorithm. Finally, based on arbitrary several sets of optimization solutions and empirical parameters, the finite element model of shafting is established for simulation, and the results show that the optimized solution has certain guiding significance for the design of the rotor system.The cooling device is designed and simulated by CFD method based on the optimal solution set. Both the inlet boundary conditions of given pressure (1 MPα) and given mass flow rate (0.1 kg/s) numerical calculations were carried out to characterize the cooling performance, for different jet impingement configurations (Hr/din = 0.0125 ∼ 5).Several sets of analyses show the strong effects of the jet-to-target spacing (Hr/din) on the rotor thermal performance at a given diameter (din) of the nozzle. Average temperature (Tc) at the free end of the rotor show that, as jet-to-target distance decreases (0.0125 ≤ Hr/din ≤ 0.33), the heat dissipation efficiency of the cooling device with the given pressure boundary condition tends to decrease, while the conclusion is opposite when the inlet boundary condition is set to the given mass flow rate. And there is an interval for the optimal combination (Hr/din) to promote the cooling efficiency.

scholarly journals Engine Performance of a Gardener Compression Ignition Engine using Rapeseed Methyl Esther

2019 ◽  
Vol 4 (2) ◽  
Author(s):  
Hamisu A Dandajeh ◽  
Talib O Ahmadu
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Equivalence Ratio ◽  
Engine Speed ◽  
Engine Performance ◽  
Combustion Characteristics ◽  
Compression Ignition ◽  
Compression Ignition Engine ◽  
Air Mass

This paper presents an experimental investigation on the influence of engine speed on the combustion characteristics of a Gardener compression ignition engine fueled with rapeseed methyl esther (RME). The engine has a maximum power of 14.4 kW and maximum speed of 1500 rpm. The experiment was carried out at speeds of 750 and 1250 rpm under loads of 4, 8, 12, 16 and 18 kg. Variations of cylinder pressure with crank angle degrees and cylinder volume have been examined. It was found that RME demonstrated short ignition delay primarily due to its high cetane number and leaner fuel properties (equivalence ratio (φ) = 0.22 at 4kg). An increase in thermal efficiency but decrease in volumetric efficiency was recorded due to increased brake loads. Variations in fuel mass flow rate, air mass flow rate, exhaust gas temperatures and equivalence ratio with respect to brake mean effective pressure at engine speeds of 750 and 1250 rpm were also demonstrated in this paper. Higher engine speed of 1250 rpm resulted in higher fuel and air mass flow rates, exhaust temperature, brake power and equivalent ratio but lower volumetric efficiency. Keywords— combustion characteristics, engine performance, engine speed, rapeseed methyl Esther

scholarly journals Off-Design Performances of an Organic Rankine Cycle for Waste Heat Recovery from Gas Turbines

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1105 ◽  
Author(s):  
Carlo Carcasci ◽  
Lapo Cheli ◽  
Pietro Lubello ◽  
Lorenzo Winchler
Keyword(s):  
Gas Turbine ◽  
Mass Flow Rate ◽  
Air Temperature ◽  
Mass Flow ◽  
Flow Rate ◽  
Power Output ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Ambient Air ◽  
Air Mass

This paper presents an off-design analysis of a gas turbine Organic Rankine Cycle (ORC) combined cycle. Combustion turbine performances are significantly affected by fluctuations in ambient conditions, leading to relevant variations in the exhaust gases’ mass flow rate and temperature. The effects of the variation of ambient air temperature have been considered in the simulation of the topper cycle and of the condenser in the bottomer one. Analyses have been performed for different working fluids (toluene, benzene and cyclopentane) and control systems have been introduced on critical parameters, such as oil temperature and air mass flow rate at the condenser fan. Results have highlighted similar power outputs for cycles based on benzene and toluene, while differences as high as 34% have been found for cyclopentane. The power output trend with ambient temperature has been found to be influenced by slope discontinuities in gas turbine exhaust mass flow rate and temperature and by the upper limit imposed on the air mass flow rate at the condenser as well, suggesting the importance of a correct sizing of the component in the design phase. Overall, benzene-based cycle power output has been found to vary between 4518 kW and 3346 kW in the ambient air temperature range considered.

Experimental Study of Spray Flame Characteristics in Hot-Diluted Oxidant Through Advanced Image Processing Technique

2017 ◽  
Author(s):  
Yuan Li ◽  
Hao Zhou ◽  
Ning Li ◽  
Kefa Cen
Keyword(s):  
Image Processing ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Air Mass ◽  
Fuel Flow ◽  
Spray Flame ◽  
Oxygen Concentrations

This paper presents a study of ethanol jet spray flame characteristics in a hot-diluted oxidant with different co-flow oxygen concentrations and fuel/air mass flow rate ratios (MF/MA ratios) through advance image processing technique. An air-blast atomizer was located in a McKenna burner which was utilized to provide stable combustion surroundings and variable combustion atmosphere for ethanol jet spray. The co-flow oxygen concentrations were set to 5%, 10%, 15% and 21% (by volume) by adjusting the mass flow rates of CH4, O2 and N2. The MF/MA ratios were set to 0.245, 0.490, 0.735, and 0.980 by adjusting the fuel mass flow rate and the carrier air mass flow rate. A high-speed RGB CCD camera was employed to capture spray flame images continuously. Spray flame edge is detected using an auto-adaptive edge-detection algorithm which could detect the spray flame edge continuously and clearly. A flame zone is defined as the region surrounded by the detected flame edge to obtain flame parameters. Spray flame characteristics are described using the measured flame parameters, involving flame area, length, brightness, nonuniformity and temperature which are derived from the spray flame images. Spray flame area, length, brightness and nonuniformity are extracted through image processing technique directly. Moreover, two-dimensional (2D) temperature profiling of spray flame is obtained by coupling image processing technique with two-color pyrometry based on Planck’s radiation law. The effects of co-flow oxygen concentration and MF/MA ratio on spray flame characteristics are investigated in this work. The spray flame parameters are observed to be sensitive to both co-flow oxygen concentration and MF/MA ratio. The results show that the fuel mass flow rate (MF) has opposite effects on spray flame characteristics compared with the carrier air mass flow rate (MA) in hot-diluted oxidant. Spray flame area and length are shown to decrease for higher co-flow oxygen concentrations, while spray flame brightness, uniformity and temperature are observed to increase for higher co-flow oxygen concentrations, owing to the enhancement of the combustion rate. A higher MF/MA ratio leads to higher spray flame area, length, brightness, uniformity and temperature, due to the increase of the droplet residence time or droplet concentration in hot-diluted oxidant. In the same MF/MA ratio, spray flame area and length are found to be smaller at a higher fuel flow rate (or carrier air flow rate). However, spray flame brightness, uniformity and temperature are demonstrated to be enhanced at a higher fuel flow rate (or carrier air flow rate). (CSPE)

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