scholarly journals Comments on “Analysis of heat transfer and irreversibility of ORC evaporator for selecting working fluid and operating conditions”

2020 ◽  
Vol 24 (4) ◽  
pp. 2661-2663 ◽  
Author(s):  
Mohamed Awad
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Graphical Method ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pinch Point ◽  
Temperature Heat ◽  
Performance Of Heat Transfer ◽  
Diagram Analysis

Commentaries are presented on Ye et al. [1]?s paper, where the authors investigated the performance of heat transfer in evaporator under the case that the parameters of the heat source and temperature of pinch point were identified. They utilized the graphical method of temperature-heat (T-Q) diagram analysis. Also, they utilized the entransy principle in their analysis. Commentaries show the reality that the graphical method of T-Q diagram analysis belongs to Professor Adrian Bejan, who first proposed it in 1977. In addition, many instances in the literature are given to indicate disputes for the entransy principle by oppositionists of ?entransy? from various countries.

A New Combined Power and Cooling Cycle for Low Temperature Heat Sources

2003 ◽  
Author(s):  
D. Y. Goswami ◽  
Gunnar Tamm ◽  
Sanjay Vijayaraghavan
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
Waste Heat ◽  
Experimental System ◽  
Operating Conditions ◽  
Working Fluid ◽  
Second Law ◽  
Heat Sources ◽  
Vapor Generation ◽  
Temperature Heat

A new thermodynamic cycle has been developed for the simultaneous production of power and cooling from low temperature heat sources. The proposed cycle combines the Rankine and absorption refrigeration cycles, providing power and cooling in desired ratios to best suit the application. A binary mixture of ammonia and water is used as the working fluid, providing a good thermal match with the sensible heat source over a range of boiling temperatures. Due to its low boiling point, the ammonia-rich vapor expands to refrigeration temperatures while work is extracted through the turbine. Absorption condensation of the vapor back into the bulk solution occurs near ambient temperatures. The proposed cycle is suitable as a bottoming cycle using waste heat from conventional power generation systems, or can utilize low temperature solar or geothermal renewable resources. The cycle can be scaled to residential, commercial or industrial uses, providing power as the primary goal while satisfying some of the cooling requirements of the application. The cycle is under both theoretical and experimental investigations. Initial parametric studies of how the cycle performs at various operating conditions showed the potential for the cycle to be optimized. Optimization studies performed over a range of heat source and heat sink temperatures showed that the cycle could be optimized for maximum work or cooling output, or for first or second law efficiencies. Depending on the heat source temperatures, as much as half of the output may be obtained as refrigeration under optimized conditions, with refrigeration temperatures as low as 205 K being achievable. Maximum second law efficiencies over 60% have been found with the heat source between 350 and 450 K. An experimental system was constructed to verify the theoretical results and to demonstrate the feasibility of the cycle. The investigation focused on the vapor generation and absorption processes, setting up for the power and refrigeration studies to come later. The turbine was simulated with an equivalent expansion process in this initial phase of testing. Results showed that the vapor generation and absorption processes work experimentally, over a range of operating conditions and in simulating the sources and sinks of interest. The potential for combined work and cooling output was evidenced in operating the system. Comparison to ideally simulated results verified that there are thermal and flow losses present, which were assessed to make both improvements in the experimental system and modifications in the simulations to include realistic losses.

scholarly journals Comparison of the Trilateral Flash Cycle and Rankine Cycle with Organic Fluid Using the Pinch Point Temperature

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1197
Author(s):  
Kai-Yuan Lai ◽  
Yu-Tang Lee ◽  
Miao-Ru Chen ◽  
Yao-Hsien Liu
Keyword(s):  
Low Temperature ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Heat Extraction ◽  
Working Fluid ◽  
Pinch Point ◽  
Temperature Heat

Low-temperature heat utilization can be applied to waste heat from industrial processes or renewable energy sources such as geothermal and ocean energy. The most common low-temperature waste-heat recovery technology is the organic Rankine cycle (ORC). However, the phase change of ORC working fluid for the heat extraction process causes a pinch-point problem, and the heat recovery cannot be efficiently used. To improve heat extraction and power generation, this study explored the cycle characteristics of the trilateral flash cycle (TFC) in a low-temperature heat source. A pinch-point-based methodology was developed for studying the optimal design point and operating conditions and for optimizing working fluid evaporation temperature and mass flow rate. According to the simulation results, the TFC system can recover more waste heat than ORC under the same operating conditions. The net power output of the TFC was approximately 30% higher than ORC but at a cost of higher pump power consumption. Additionally, the TFC was superior to ORC with an extremely low-temperature heat source (<80 °C), and the ideal efficiency was approximately 3% at the highest work output condition. The TFC system is economically beneficial for waste-heat recovery for low-temperature heat sources.

scholarly journals Analysis and Comparison of Some Low-Temperature Heat Sources for Heat Pumps

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1853 ◽  
Author(s):  
Pavel Neuberger ◽  
Radomír Adamovský
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Heat Source ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Ambient Air ◽  
Heat Transfer Fluid ◽  
Heat Sources ◽  
Ground Heat Exchangers ◽  
Temperature Heat

The efficiency of a heat pump energy system is significantly influenced by its low-temperature heat source. This paper presents the results of operational monitoring, analysis and comparison of heat transfer fluid temperatures, outputs and extracted energies at the most widely used low temperature heat sources within 218 days of a heating period. The monitoring involved horizontal ground heat exchangers (HGHEs) of linear and Slinky type, vertical ground heat exchangers (VGHEs) with single and double U-tube exchanger as well as the ambient air. The results of the verification indicated that it was not possible to specify clearly the most advantageous low-temperature heat source that meets the requirements of the efficiency of the heat pump operation. The highest average heat transfer fluid temperatures were achieved at linear HGHE (8.13 ± 4.50 °C) and double U-tube VGHE (8.13 ± 3.12 °C). The highest average specific heat output 59.97 ± 41.80 W/m2 and specific energy extracted from the ground mass 2723.40 ± 1785.58 kJ/m2·day were recorded at single U-tube VGHE. The lowest thermal resistance value of 0.07 K·m2/W, specifying the efficiency of the heat transfer process between the ground mass and the heat transfer fluid, was monitored at linear HGHE. The use of ambient air as a low-temperature heat pump source was considered to be the least advantageous in terms of its temperature parameters.

scholarly journals Fast three-dimensional heat transfer model for computing internal temperatures in the bearing housing of automotive turbochargers

2018 ◽  
Vol 21 (8) ◽  
pp. 1286-1297 ◽  
Author(s):  
Antonio Gil ◽  
Andrés Omar Tiseira ◽  
Luis Miguel García-Cuevas ◽  
Tatiana Rodríguez Usaquén ◽  
Guillaume Mijotte
Keyword(s):  
Heat Transfer ◽  
Coke Formation ◽  
Three Dimensional ◽  
Heat Transfer Model ◽  
Operating Conditions ◽  
Thermal Design ◽  
Working Fluid ◽  
Transfer Model ◽  
Lumped Model ◽  
Bearing System

Each of the elements that make up the turbocharger has been gradually improved. In order to ensure that the system does not experience any mechanical failures or loss of efficiency, it is important to study which engine-operating conditions could produce the highest failing rate. Common failing conditions in turbochargers are mostly achieved due to oil contamination and high temperatures in the bearing system. Thermal management becomes increasingly important for the required engine performance. Therefore, it has become necessary to have accurate temperature and heat transfer models. Most thermal design and analysis codes need data for validation; often the data available fall outside the range of conditions the engine experiences in reality leading to the need to interpolate and extrapolate disproportionately. This article presents a fast three-dimensional heat transfer model for computing internal temperatures in the central housing for non-water cooled turbochargers and its direct validation with experimental data at different engine-operating conditions of speed and load. The presented model allows a detailed study of the temperature rise of the central housing, lubrication channels, and maximum level of temperature at different points of the bearing system of an automotive turbocharger. It will let to evaluate thermal damage done to the system itself and influences on the working fluid temperatures, which leads to oil coke formation that can affect the performance of the engine. Thermal heat transfer properties obtained from this model can be used to feed and improve a radial lumped model of heat transfer that predicts only local internal temperatures. Model validation is illustrated, and finally, the main results are discussed.

Effect of non-uniform heat source/sink on MHD boundary layer flow and melting heat transfer of Williamson nanofluid in porous medium

2019 ◽  
Vol 15 (2) ◽  
pp. 452-472 ◽  
Author(s):  
Jayarami Reddy Konda ◽  
Madhusudhana Reddy N.P. ◽  
Ramakrishna Konijeti ◽  
Abhishek Dasore
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Heat Source ◽  
Radiation Effects ◽  
Navier Stokes ◽  
Working Fluid ◽  
Content Type ◽  
Linear Ordinary Differential Equations ◽  
Uniform Heat ◽  
Source Sink

PurposeThe purpose of this paper is to examine the influence of magnetic field on Williamson nanofluid embedded in a porous medium in the presence of non-uniform heat source/sink, chemical reaction and thermal radiation effects.Design/methodology/approachThe governing physical problem is presented using the traditional Navier–Stokes theory. Consequential system of equations is transformed into a set of non-linear ordinary differential equations by means of scaling group of transformation, which are solved using the Runge–Kutta–Fehlberg method.FindingsThe working fluid is examined for several sundry parameters graphically and in a tabular form. It is noticed that with an increase in Eckert number, there is an increase in velocity and temperature along with a decrease in shear stress and heat transfer rate.Originality/valueA good agreement of the present results has been observed by comparing with the existing literature results.

Calculation and Optimization of Heat Transfer between the Low Exergy Heat Source and Organic Rankine Cycle Applied to Heat Recovery Systems

2013 ◽  
Vol 597 ◽  
pp. 45-50
Author(s):  
Sławomir Smoleń ◽  
Hendrik Boertz
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Heat Recovery ◽  
Power Plants ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Optimization Procedure ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Total System

One of the key challenges on the area of energy engineering is the system development for increasing the efficiency of primary energy conversion and use. An effective and important measure suitable for improving efficiencies of existing applications and allowing the extraction of energy from previously unsuitable sources is the Organic Rankine Cycle. Applications based on this cycle allow the use of low temperature energy sources such as waste heat from industrial applications, geothermal sources, biomass, fired power plants and micro combined heat and power systems.Working fluid selection is a major step in designing heat recovery systems based on the Organic Rankine Cycle. Within the framework of the previous original study a special tool has been elaborated in order to compare the influence of different working fluids on performance of an ORC heat recovery power plant installation. A database of a number of organic fluids has been developed. The elaborated tool should create a support by choosing an optimal working fluid for special applications and become a part of a bigger optimization procedure by different frame conditions. The main sorting criterion for the fluids is the system efficiency (resulting from the thermo-physical characteristics) and beyond that the date base contains additional information and criteria, which have to be taken into account, like environmental characteristics for safety and practical considerations.The presented work focuses on the calculation and optimization procedure related to the coupling heat source – ORC cycle. This interface is (or can be) a big source of energy but especially exergy losses. That is why the optimization of the heat transfer between the heat source and the process is (besides the ORC efficiency) of essential importance for the total system efficiency.Within the presented work the general calculation approach and some representative calculation results have been given. This procedure is a part of a complex procedure and program for Working Fluid Selection for Organic Rankine Cycle Applied to Heat Recovery Systems.

Single-Phase Heat Transfer and Pressure Drop of Water Cooled Inside Horizontal Smooth Tubes in the Transitional Flow Regime

2010 ◽  
Author(s):  
Josua P. Meyer ◽  
Leon Liebenberg ◽  
Jonathan A. Olivier
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Transition Region ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Transitional Flow ◽  
Working Fluid ◽  
Tube Heat Exchanger ◽  
Smooth Tubes

Heat exchangers are usually designed in such a way that they do not operate in the transition region. This is usually due to a lack of information in this region. However, due to design constraints, energy efficiency requirements or change of operating conditions, heat exchangers are often forced to operate in this region. It is also well known that entrance disturbances influence where transition occurs. The purpose of this paper is to present experimental heat transfer and pressure drop data in the transition region for fully developed and developing flows inside smooth tubes using water as the working fluid. The use of different inlet disturbances were used to investigate its effect on transition. A tube-in-tube heat exchanger was used to perform the experiments, which ranged in Reynolds numbers from 1 000 to 20 000, with Prandtl numbers being between 4 and 6 while Grashof numbers were in the order of 105. Results showed that the type of inlet disturbance could delay transition to a Reynolds number as high as 7 000, while other inlets expedited it, confirming results of others. For heat transfer, though, it was found that transition was independent of the inlet disturbance and all commenced at the same Reynolds number, 2 000–3 000, which was attributed to secondary flow effects.

scholarly journals Experimental Investigation of Embedded Micropin-Fins for Single-Phase Heat Transfer and Pressure Drop

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Chirag R. Kharangate ◽  
Ki Wook Jung ◽  
Sangwoo Jung ◽  
Daeyoung Kong ◽  
Joseph Schaadt ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Friction Factor ◽  
Integrated Circuit ◽  
Single Phase ◽  
Absolute Error ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pin Fin

Three-dimensional (3D) stacked integrated circuit (IC) chips offer significant performance improvement, but offer important challenges for thermal management including, for the case of microfluidic cooling, constraints on channel dimensions, and pressure drop. Here, we investigate heat transfer and pressure drop characteristics of a microfluidic cooling device with staggered pin-fin array arrangement with dimensions as follows: diameter D = 46.5 μm; spacing, S ∼ 100 μm; and height, H ∼ 110 μm. Deionized single-phase water with mass flow rates of m˙ = 15.1–64.1 g/min was used as the working fluid, corresponding to values of Re (based on pin fin diameter) from 23 to 135, where heat fluxes up to 141 W/cm2 are removed. The measurements yield local Nusselt numbers that vary little along the heated channel length and values for both the Nu and the friction factor do not agree well with most data for pin fin geometries in the literature. Two new correlations for the average Nusselt number (∼Re1.04) and Fanning friction factor (∼Re−0.52) are proposed that capture the heat transfer and pressure drop behavior for the geometric and operating conditions tested in this study with mean absolute error (MAE) of 4.9% and 1.7%, respectively. The work shows that a more comprehensive investigation is required on thermofluidic characterization of pin fin arrays with channel heights Hf < 150 μm and fin spacing S = 50–500 μm, respectively, with the Reynolds number, Re < 300.

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.

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