scholarly journals FACTORS OF THE PVT-COLLECTOR EFFICIENCY FORMATION

2021 ◽  
Vol 1 (63) ◽  
pp. 53-59
Author(s):  
V. Wysochin ◽  
◽  
V. Nikulshin ◽  
A. Denysova ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Thermal Energy ◽  
Optimization Problems ◽  
Cooling System ◽  
Operating Conditions ◽  
Heat Transfer Agent ◽  
Local Analysis ◽  
Limit Values ◽  
Method Of Calculation

Analytical researches of a hybrid solar collecting channel (PVT) are conducted by manufacture electric and thermal energy. The method of researches allows to analyse the following PVT-collector characteristics : a reheat temperature of an absorber and chilling liquid, as well as productivity depending on external and regime working conditions of the device. The work purpose is to work out of a method of calculation of opeating characteristics and definition of rational operating conditions of work of a hybrid solar collecting channel taking into account effective productivity. The complex mathematical model of the local analysis of processes of heat exchange and electrogeneration of a hybrid solar collecting channel for real conditions of a dynamic solar and climatic situation is used. The carried out analysis of heat exchange in alternative conditions showed that efficiency of a heat transport in a collecting channel integral cooling system ηT (a relationship of temperature of an absorber and final temperature of heat-transfer agent) is not a constant and considerably changes under the external and internal factors. It is influenced by intensity of insolation and the heat-transfer agent charge. With growth of these parametres ηT decreases. Existing dependence of electric power of a photo cell on the charge of a chilling liquid is characterised by presence of two expressed sections which are discriminated by rate of a variation of a function. The first of them, with low flux level of a liquid, differs considerable agency of functional parametres. The second one at high intensity differs asymptotic stabilisation of power. The limit values of the transition of the rate of decrease of the function correspond to the fluid flow rate of 0.08...0.085 l/(m2s). These values can be accepted for rationalisation of a refrigerating duty of the photobattery. Generalized dependences for determining the temperature of the liquid at the outlet of the device and the average temperature of the absorber are obtained. These dependences can be used to evaluate the efficiency of conversion of solar energy into electrical and thermal energy in regime optimization problems.

scholarly journals Test Results of a Polymer Radiator of MTZ-80 Tractor Cooling System

2020 ◽  
Vol 14 (1) ◽  
pp. 55-60
Author(s):  
O. N. Didmanidze ◽  
R. T. Khakimov ◽  
E. P. Parlyuk ◽  
N. A. Bol’shakov
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Cooling System ◽  
Operating Mode ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Hydrodynamic Resistance ◽  
Measuring Instruments ◽  
Research Areas ◽  
In Series

Global car manufacturers wish to increase the number of manufactured products, reduce their cost and labor input. The choice of research areas, design and technological developments in radiator construction is an extremely important and urgent task, due to the mass production of radiators for tractors and automobiles on the one hand, and the favorable development prospects of these interrelated industries, on the other. (Research purpose) To substantiate theoretically and experimentally the use of a combined cooling system containing both aluminum and polymeric water radiators and similarly liquid-oil heat exchangers based on the four principles listed above on automobiles and tractors. (Materials and methods) The authors performed bench tests using a special wind tunnel to study the thermal and aerodynamic characteristics of a prototype tractor radiator with a polyurethane core. After reaching the steady-state operating mode of the installation, the experimental values were determined for the control and measuring instruments. (Results and discussion) The authors carried out measurements of all parameters of both coolants in series at each steady-state operating mode of the bench. They obtained the main indicators dependences (reduced heat transfer, aerodynamic and hydraulic drag) of the heat exchanger, close to the operating conditions of the vehicles. (Conclusions) A prototype MTZ-80 radiator with a polyurethane core has great prospects as a future alternative radiator. An increase by 10-15 percent in the radiator heat transfer is possible by using aluminum fi ns on the surface of the polyurethane plate. A 15-20 percent reduction in hydrodynamic resistance is achieved by increasing the diameter of the capillary throughput in a polyurethane plate and the number of plates themselves in the radiator cell.

scholarly journals Full Surface Heat Transfer Characteristics of Stator Ventilation Duct of a Turbine Generator

2020 ◽  
Author(s):  
Shinyoung Jeon ◽  
Changmin Son ◽  
Jangsik Yang
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Cross Flow ◽  
Surface Heat ◽  
Operating Conditions ◽  
Scale Model ◽  
Turbine Generator ◽  
Surface Heat Transfer ◽  
Ventilation Duct ◽  
Flow Case

Turbine generator operates with complex cooling system due to the challenge in controlling the peak temperature of the stator bar caused by ohm loss, which is unavoidable. Therefore, it is important to characterise and quantifies the thermal performance of the cooling system. The focus of the present research is to investigate the heat transfer and pressure loss characteristics of typical cooling system, so-called stator ventilation duct. A real scale model was built at its operating conditions for the present study. The direction of cooling air is varied to consider its operation condition, so that there are (1) outward flow and (2) inward flow cases. In addition, the effect of (3) cross flow (inward with cross flow case) is also studied. The transient heat transfer method using thermochromic liquid crystals is implemented to measure full surface heat transfer distribution. A series of Computational Fluid Dynamics analysis is also conducted to support the observation from the experiment. For the inward flow case, the results suggest that the average Nusselt number of the 2nd duct is about 30% higher than the 3rd duct. The trend is similar with the effect of cross flow. The CFD results are in good agreement with the experimental data.

The Effects of Spraying Parameters on Spray Cooling Heat Transfer Performance in the Non-Boiling Regime

2017 ◽  
Author(s):  
Azzam S. Salman ◽  
Jamil A. Khan
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Target Surface ◽  
Spray Cooling ◽  
Operating Conditions ◽  
Droplet Velocity ◽  
Inlet Pressure ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Spraying Parameters

Experiments were conducted in a closed loop spray cooling system working with deionized water as a working fluid. This study was performed to investigate the effect of the spraying parameters, such as Sauter mean diameter (SMD), the droplet velocity, and the residual velocity on the spray cooling heat transfer in the non-boiling region. Thermal effects on plain and modified surfaces with circular grooves were examined under different operating conditions. The inlet pressure of the working fluid was varied from 78.6 kPa to 183.515kPa, and the inlet temperature was kept between 21–22 °C. The distance between the nozzle and the target surface 10 mm. The results showed that increasing the coolant inlet pressure increases the droplet velocity and the number of droplets produced while decreasing the droplet size. As a consequence of these changes, increasing inlet pressure improved the heat transfer characteristics of both surfaces.

Steady and Unsteady Modeling for Heat Transfer Predictions of High Pressure Turbine Blade Internal Cooling

2012 ◽  
Author(s):  
Rémy Fransen ◽  
Nicolas Gourdain ◽  
Laurent Y. M. Gicquel
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Cooling System ◽  
Transfer Problem ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Wall Region ◽  
Internal Cooling ◽  
Computational Domain ◽  
Complex Flow

This work focuses on numerical simulations of flows in blade internal cooling system. Large Eddy Simulation (LES) and Reynolds-Averaged Navier Stokes (RANS) approaches are compared in a typical blade cooling related problem. The case is a straight rib-roughened channel with high blockage ratio, computed and compared for both a periodic and full spatial domains. The configuration was measured at the Von Karman Institute (VKI) using Particle Image Velocimetry (PIV) in near gas turbine operating conditions. Results show that RANS models used fail to predict the full evolution of the flow within the channels where massive separation and large scale unsteady features are evidenced. In contrast LES succeeds in reproducing these complex flow motions and both mean and fluctuating components are clearly improved in the channels and in the near wall region. Periodic computations are gauged against the spatial computational domain and results on the heat transfer problem are addressed.

scholarly journals A Numerical Analysis of the Air-Cooling System of a Spark Ignition Aeronautical Engine

2020 ◽  
Vol 197 ◽  
pp. 06003
Author(s):  
Maria Faruoli ◽  
Annarita Viggiano ◽  
Paolo Caso ◽  
Vinicio Magi
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Cooling System ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Air Cooling ◽  
Air Mass ◽  
Air Cooling System

It is well known that spark ignition internal combustion engines for aeronautical applications operate within a specific temperature range to avoid structural damages, detonations and loss of efficiency of the combustion process. An accurate assessment of the cooling system performance is a crucial aspect in order to guarantee broad operating conditions of the engine. In this framework, the use of a Conjugate Heat Transfer method is a proper choice, since it allows to estimate both the heat fluxes between the engine walls and the cooling air and the temperature distribution along the outer wall surfaces of the engine, and to perform parametric analyses by varying the engine operating conditions. In this work, the air-cooling system of a 4-cylinder spark ignition engine, designed by CMD Engine Company for aeronautical applications, is analysed in order to evaluate the amount of the air mass flow rate to guarantee the heat transfer under full load operating conditions. A preliminary validation of the model is performed by comparing the results with available experimental data. A parametric study is also performed to assess the influence of the controlling parameters on the cooling system efficiency. This study is carried out by varying the inlet air mass flow rate from 1.0 kg/s to 1.5 kg/s and the temperature of the inner wall surfaces of the engine combustion chambers from 390 K to 430 K.

scholarly journals Simulation of a Solar-Assisted Air-Conditioning System Applied to a Remote School

2019 ◽  
Vol 9 (16) ◽  
pp. 3398 ◽  
Author(s):  
Jesús Armando Aguilar-Jiménez ◽  
Nicolás Velázquez ◽  
Ricardo López-Zavala ◽  
Luis A. González-Uribe ◽  
Ricardo Beltrán ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
Thermal Energy ◽  
Cooling Tower ◽  
Cooling System ◽  
Maximum Load ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Solar Thermal Energy ◽  
Heating And Cooling ◽  
Cooling Coils

In this work, we present an absorption cooling system with 35 kW capacity driven by solar thermal energy, installed in the school of Puertecitos, Mexico, an off-grid community with a high level of social marginalization. The cooling system provides thermal comfort to the school’s classrooms through four 8.75-kW cooling coils, while a 110-m2 field of evacuated tube solar collectors delivers the thermal energy needed to activate the cooling machine. The characteristics of the equipment installed in the school were used for simulation and operative analysis of the system under the influence of typical factors of an isolated coastal community, such as the influence of climate, thermal load, and water consumption in the cooling tower, among others. The aim of this simulation study was to determine the best operating conditions prior to system start-up, to establish the requirements for external heating and cooling services, and to quantify the freshwater requirements for the proper functioning of the system. The results show that, with the simulated strategies implemented, with a maximum load operation, the system can maintain thermal comfort in the classrooms for five days of classes. This is feasible as long as weekends are dedicated to raising the water temperature in the thermal storage tank. As the total capacity of the system is distributed in the four cooling coils, it is possible to control the cooling demand in order to extend the operation periods. Utilizing 75% or less of the cooling capacity, the system can operate continuously, taking advantage of stored energy. The cooling tower requires about 750 kg of water per day, which becomes critical given the scarcity of this resource in the community.

Computer 2D modelling of a micro-grip fluid cooling system

2021 ◽  
pp. 4-20
Author(s):  
Ильдар Шамилевич Насибуллаев ◽  
Олег Владимирович Даринцев
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchange ◽  
Transfer Coefficient ◽  
Cooling System ◽  
Fluid Velocity ◽  
Physical Parameters ◽  
Peltier Element ◽  
Fluid Cooling ◽  
Flow Frequency

Представлено компьютерное численное моделирование системы жидкостного охлаждения камеры микрозахвата. Построены математические модели течения жидкости, переноса тепла жидкостью, теплообмена между жидкостью и радиатором, теплообмена между радиатором и элементом Пельтье. Определено влияние геометрических и физических параметров камеры микрозахвата на эффективность системы охлаждения, а также найдена зависимость максимальной температуры, установившейся на радиаторе, от скорости течения охлаждающей жидкости и коэффициента теплопередачи между радиатором и жидкостью для стационарного течения. Проведено исследование влияния нестационарного течения жидкости на колебания температуры радиатора. На основе результатов численного моделирования предложены простые аналитические формулы, которые можно использовать в программном обеспечении системы управления микрозахватом Numerical simulation of a micro-grip chamber fluid cooling system is presented. The mathematical models for mass and heat transfer in a fluid, heat exchange between the fluid and the radiator as well as the heat exchange between the radiator and the Peltier element are constructed in a variational form. The equations of hydrodynamics and heat equations were simulated by the finite element method in the FreeFem++ software. The influence of the geometric and physical parameters of the cooling system chamber on the efficiency of the device is determined. It is shown that as the heat transfer coefficient between the radiator and the fluid and the velocity of the coolant increases, the maximum steady-state temperature on the radiator nonlinearly decreases with saturation. When flow of coolant oscillates then the temperature on the radiator so does with the flow frequency. As the flow frequency increases, the amplitude of temperature fluctuations decreases. The increasing amplitude of flow oscillations leads to the amplification of the temperature amplitude. Using orthogonal central compositional method, the influence of the parameters (heat transfer coefficient, fluid velocity) on the efficiency of the cooling system is found, and the contribution of pairwise interaction is determined. Based on the results of numerical modelling, simple analytical formulas are proposed that can be used in the software module of the micro-grip cooling control system.

Flow and heat transfer in a closed loop thermosyphon Part II – experimental simulation

2007 ◽  
Vol 18 (4) ◽  
pp. 41-48 ◽  
Author(s):  
J.C. Ruppersberg ◽  
R.T. Dobson
Keyword(s):  
Heat Transfer ◽  
Closed Loop ◽  
Cooling System ◽  
Operating Conditions ◽  
Experimental Simulation ◽  
Theoretical Modelling ◽  
Working Fluid ◽  
Small Scale ◽  
System A ◽  
Test Loop

A closed loop thermosyphon is an energy transfer device that employs thermally induced density gra-dients to induce circulation of the working fluid thereby obviating the need for any mechanical moving parts such as pumps and pump controls. This increases the reliability and safety of the cool-ing system and reduces installation, operation and maintenance costs. These characteristics make it a particularly attractive option for the cavity cooling system of the Pebble Bed Modular Reactor (PBMR). Loop thermosyphons are however, known to become unstable under certain initial and operating conditions. It is therefore necessary to conduct an experimental and theoretical study of the start-up and transient behaviour of such a system. A small scale test loop was built representing a section of a concept cooling system. A number of representative yet typical experimental temperature and flow rate curves for a range of initial and boundary condi-tions were generated, plotted and are given as a function of time. These curves show that oscillatory temperature and flow occurred that was dependent on the differing design and operating conditions. A number of theoretical modelling and actual cooling system design problem areas were identified. These problem areas need to be addressed if more accu-racy is required to capture the erratic and ostensibly chaotic heat transfer behaviour of the loop.

Experimental Studies of Thermal Hydraulics of a HLMC Flow Around Heat Exchange Surfaces

2013 ◽  
Author(s):  
Mikhail Iarmonov ◽  
Olga Novozhilova ◽  
Pavel Bokov ◽  
A. V. Beznosov
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Heat Exchange ◽  
Experimental Studies ◽  
Velocity Fields ◽  
Operating Conditions ◽  
Coolant Flow ◽  
Oxygen Impurity ◽  
Lead Coolant ◽  
Temperature And Velocity Fields

Temperature and velocity fields in high-temperature lead coolant flows in a circular clearance for controlled oxygen impurity content in a flow were experimentally studied at the Nizhny Novgorod State Technical University by R.E. Alekseev (NNSTU). Temperature and velocity fields were simultaneously studied in “cold” and “hot” parts of the circuit in the following operating conditions: the lead temperature is t = 400–550 °C, the thermodynamic activity of oxygen is a = 10−5–100; the Peclet number is Pe = 500–7000, the coolant flow velocity is w = 0.1–1.5 m/s, and the average heat flux is q = 50–160 kW/m2. It has been found that the oxygen impurity content and characteristics of protective oxide coatings affect temperature and velocity fields in round and circular channels. This is due to the fact that oxygen in a coolant and oxide coatings on the surfaces limiting a liquid metal flow influence characteristics of the wall boundary region. The heat transfer process that occurs when HLMC transversely flows around heat exchange pipes is investigated now at the NNSTU. The experimental facility is a combination of two high-temperature liquid-metal stands, i.e., FT-2 with the lead coolant and FT-1 with the lead-bismuth coolant combined with an experimental section. The temperature of a heat-exchange surface is measured by thermocouples of diameter 1 mm mounted in walls of heat-exchange pipes. Velocity and temperature fields in a high-temperature HLMC flow are measured by special sensors placed in the flow cross section between rows of heat-exchange pipes. Heat transfer characteristics and temperature and velocity fields in a high-temperature lead coolant flow are studied in the following operating conditions: the lead temperature is t = 450–500 °C, the thermodynamic activity of oxygen is a = 10−5–100, and the coolant flow rate through the experimental setup is Q = 3–6 m3/h, which corresponds to coolant flow velocities of V = 0.4–0.8 m/s. Integrated experimental studies of characteristics of the heat transfer that occurs when the lead coolant transversely or obliquely flows around pipes have been carried out for the first time and the dependences Nu = f(Pe) for controlled content of thermodynamically active oxygen impurity and sediments of impurities have been obtained. It is assumed that the obtained experimental data on distribution of velocity and temperature fields in a HLMC flow will permit to study heat transfer processes and to use them for developing program codes for engineering calculations of heat exchange surfaces (steam generators) with a HLMC flow around them.

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