An Analysis of the Ideal Otto Cycle, Including the Effects of Heat Transfer, Finite Combustion Rates, Chemical Dissociation, and Mechanical Losses

1964 ◽  
pp. 92-105 ◽  
Author(s):  
F.M. Strange
Keyword(s):  
Heat Transfer ◽  
Otto Cycle ◽  
The Ideal

Heat Flux Sensor With Minimal Impact on Boundary Conditions

2003 ◽  
Author(s):  
Arash Saidi ◽  
Jungho Kim
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Flux ◽  
Heat Flux Sensor ◽  
Inverse Heat Conduction ◽  
Minimal Impact ◽  
Sensor Performance ◽  
Flow Through ◽  
Flux Sensor ◽  
The Ideal

A technique for determining the heat transfer on the far surface of a wall based on measuring the heat transfer and temperature on the near wall is presented. Although heat transfer measurements have previously been used to augment temperature measurements in inverse heat conduction methods, the sensors used alter the heat flow through the surface, disturbing the very quantity that is desired to be measured. The ideal sensor would not alter the boundary condition that would exist were the sensor not present. The innovation of this technique in that it has minimal impact on the wall boundary condition. Since the sensor is placed on the surface of the wall, no alteration of the wall is needed. The theoretical basis for the experimental technique as well as experimental results showing the heat flux sensor performance is presented.

scholarly journals ANALYSIS OF EVAPORATOR EFFECTIVENESS ON 1/2 CYCLE REFRIGERATION SYSTEMS: A CASE STUDY ON LPG FUELED VEHICLES

2020 ◽  
Vol 82 (3) ◽  
Author(s):  
Muji Setiyo ◽  
Budi Waluyo ◽  
Nurkholis Hamidi
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Exchange Process ◽  
Cooling Curve ◽  
Heat Exchange Process ◽  
Heat Transfer Capacity ◽  
The Ideal

The ½ cycle refrigeration system on LPG fueled vehicles has a significant cooling effect. However, the cooling is very dependent on the heat exchange process in the evaporator. Therefore, this paper analyses the deviation of the actual cooling curve from the ideal scenario carried out on a laboratory scale. The analytical method used is the calculation of the effectiveness of the evaporator, which compares the actual to the potential heat transfer capacity. The LPG flow rate was varied from 1-6 g/s, while the evaporation pressure ranged between 0.05, 0.10, and 0.15 MPa, which applied to compact type evaporators with dimensions of 262 ´ 200 mm, with a thickness of 65 mm. The research results confirm that the higher the LPG mass flow rate, the lower the heat transfer effectiveness. At the higher LPG mass flow rate, heat transfer occurs less optimally,  due to incomplete evaporation of LPG in the evaporator.

scholarly journals Review of improvements on heat transfer using nanofluids via corrugated facing step

2018 ◽  
Vol 7 (4.13) ◽  
pp. 160 ◽  
Author(s):  
Ali Hilo ◽  
Abd Rahim Abu Talib ◽  
Sadeq R. Nfawa ◽  
Mohamed Thariq Hameed Sultan ◽  
Mohd Faisal Abdul Hamid
Keyword(s):  
Heat Transfer ◽  
Thermal Conduction ◽  
Experimental Studies ◽  
Conductivity Measurement ◽  
Measurement Methods ◽  
Laminar Flows ◽  
Transfer Enhancement ◽  
Innovative Design ◽  
Experimental Findings ◽  
The Ideal

Nanofluids are considered to offer significant advantages as thermodynamic fluids because of their admirable properties on thermal conduction, thermal convection, boiling heat transfer and stability. This paper presents numerous researches focusing on the improvement of heat transfer via facing step and corrugated channels using nanofluids and without it. Exploration on the convective heat transfer was done through numerical modeling. It was reported that experimental studies were carried out in corrugated and facing step channels through the application of nanofluids and conventional fluids for heat transfer enhancement. The turbulent and laminar flows along corrugated and facing step channels have been presented. The numerical and experimental findings in maximizing the heat transfer rate are in accord. Comparisons between thermal conductivity measurement methods were done. Innovative design of corrugated facing step channel is being proposed. The heat transfer enhancements reach 60% by using facing step channel under laminar flow with nanofluid. The dimensions of new channel such as height and width of the baffle, the height of the step, shape and height of corrugated are needed to compare that might to provide the ideal rate of heat transfer.  

Heat Transfer and Pressure Drop Through Nano-Fin Arrays in the Free-Molecular Flow Regime

2012 ◽  
Author(s):  
Michael James Martin
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Gas Flow ◽  
Ideal Gas ◽  
Molecular Flow ◽  
Ideal Gas Law ◽  
Transfer Equations ◽  
Flow Through ◽  
The One ◽  
The Ideal

Gas flow through arrays of rectangular nano-fins is modeled using the linearized free-molecular drag and heat transfer equations. These are combined with the one-dimensional equations for conservation of mass, momentum, and energy, and the ideal gas law, to find the governing equations for flow through the array. The results show that the pressure gradient, temperature, and local velocity of the gas are governed by coupled ordinary differential equations. The system of equations is solved for representative arrays of nano-fins to find the total heat transfer and pressure drop across a 1 cm chip.

An Explanation for Observed Compression Ratios in Internal Combustion Engines

1991 ◽  
Vol 113 (4) ◽  
pp. 511-513 ◽  
Author(s):  
S. A. Klein
Keyword(s):  
Internal Combustion Engines ◽  
Internal Combustion ◽  
Operating Conditions ◽  
Combustion Engines ◽  
Otto Cycle ◽  
Diesel Cycle ◽  
Maximum Work ◽  
The Ideal

Comparisons of the compression ratios, efficiencies, and work of the ideal Otto and Diesel cycles are presented at conditions that yield maximum work per cycle. The compression ratios that maximize the work of the Diesel cycle are found always to be higher than those for the Otto cycle at the same operating conditions, although the thermal efficiencies are nearly identical. The compression ratios that maximize the work of the Otto and Diesel cycles compare well with the compression ratios employed in corresponding production engines.

scholarly journals Thermodynamic Model for Performance Analysis of a Stirling Engine Prototype

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2655 ◽  
Author(s):  
Miguel Torres García ◽  
Elisa Carvajal Trujillo ◽  
José Vélez Godiño ◽  
David Sánchez Martínez
Keyword(s):  
Heat Transfer ◽  
Decision Making ◽  
Stirling Engine ◽  
Decision Making Process ◽  
Actual Behavior ◽  
Isothermal Model ◽  
Working Cycle ◽  
Stirling Engines ◽  
Expected Values ◽  
The Ideal

In this study, the results of simulations generated from different thermodynamic models of Stirling engines are compared, including characterizations of both instantaneous and indicated operative parameters. The aim was to develop a tool to guide the decision-making process regarding the optimization of both the performance and reliability of Stirling engines, such as the 2.9 kW GENOA 03 unit—the focus of this work. The behavior of the engine is characterized using two different approaches: an ideal isothermal model, the simplest of those available, and analysis using the ideal adiabatic model, which is more complex than the first. Some of the results obtained with the referred ideal models deviated considerably from the expected values, particularly in terms of thermal efficiency, so a set of modifications to the ideal adiabatic model are proposed. These modifications, mainly related to both heat transfer and fluid friction phenomena, are intended to overcome the limitations due to the idealization of the engine working cycle, and are expected to generate results closer to the actual behavior of the Stirling engine, despite the increase in the complexity derived from the modelling and simulation processes.

CFD Analysis of the Flow in Crud-Coated Nuclear Rod Bundles

2014 ◽  
Author(s):  
Nicolas Cinosi ◽  
Simon P. Walker ◽  
Mike Bluck ◽  
Raad I. Issa
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Flow Rate ◽  
Flow Distribution ◽  
Normal Operation ◽  
Cfd Analysis ◽  
Rod Bundles ◽  
Ideal Case ◽  
Rans Models ◽  
The Ideal

This paper presents a methodology to assess the effects of crud surface roughnesses on the normal operation of a PWR reactor. A CFD methodology based on the use of RANS models and the implementation of roughness embedded in STAR-CCM+ CFD code has been developed and applied. A typical PWR reactor case is investigated in details. Results show how the presence of crudded rough rods induces a modification of the flow distribution as compared to the ideal case with clean smooth rods. Notably, these modifications reflect a reduction of the mass flow rate, which in turn has a deteriorating consequence on the efficiency of the fuel-to-coolant heat transfer.

Numerical Analysis of Heat Transfer and Pressure Drop in Metal Foams for Different Morphological Models

2014 ◽  
Vol 136 (11) ◽  
Author(s):  
Marcello Iasiello ◽  
Salvatore Cunsolo ◽  
Maria Oliviero ◽  
William M. Harris ◽  
Nicola Bianco ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Metal Foam ◽  
High Surface ◽  
Industrial Applications ◽  
Metal Foams ◽  
The Real ◽  
Numerical Predictions ◽  
The Ideal

Because of their light weight, open porosity, high surface area per unit volume, and thermal characteristics, metal foams are a promising material for many industrial applications involving fluid flow and heat transfer. The pressure drop and heat transfer in porous media have inspired a number of experimental and numerical studies, and many models have been proposed in the literature that correlate the pressure gradient and the heat transfer coefficient with the mean cell size and porosity. However, large differences exist among results predicted by different models, and most studies are based on idealized periodic cell structures. In this study, the true three-dimensional microstructure of the metal foam is obtained by employing x-ray computed microtomography (XCT). This is the “real” structure. For comparison, ideal Kelvin foam structures are developed in the free-to-use software “surface evolver” surface energy minimization program. These are “ideal” structures. Pressure drop and heat transfer are then investigated in each structure using the CFD module of COMSOL® Multiphysics code. A comparison between the numerical predictions from the real and ideal geometries is carried out. The predictions showed that heat transfer characteristics are very close for low values of Reynolds number, but larger Reynolds numbers create larger differences between the results of the ideal and real structures. Conversely, the differences in pressure drop at any Reynolds number are nearly 100%. Results from the models are then validated by comparing them with experimental results taken from the literature. The validation suggests that the ideal structure poorly predicts the heat transfer and pressure drops.

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