EGH422 Advanced Thermodynamics

Assignment

Heat Exchanger

Simulation

Table of Contents

Introduction

Heat change device used to transfer or change heat energy for distinctive functions. In enterprise, heat exchangers are very important and play an essential function in restoring warmness among drinks of tactics. The most common devices for heat transfer are constant tube (double pipe), shell and tube as well, plate warmness exchanger. A twin-pipe warmth exchanger is a fundamental and simple warmness trade tool used to trade warmth power with a corresponding float or with an overhead float device. When the desired heat transfer vicinity is small (as much as 50 m2), a two-pipe warmth exchanger performs a chief position. Here, flow association is essential whilst one or both of the technique fluid is run at excessive strain, due to the small diameter of the pipes. When designing heat transfer system it must be stated that the change between the two conflicting objectives of low value expenses (high coefficient of low warmness transfer heat alternate) and low operating charges (low flow strain reduction). It is already defined by using the use of various numerical methods which includes NTU and LMTD techniques. However, in those methods it is computially time consuming, detecting numerical errors throughout calculation and can’t all predict hot and hydraulic conduct of beverages in the go with the flow areas. To clear up this trouble, computational fluid dynamics (CFD) software can be used. CFD is the technology of predicting the pattern of fluid glide, warmth and mass switch, chemical reactions, and occasions related to fixing a set of statistical controls inclusive of weight conservation, power conservation, power conservation, biodiversity conservation, physiological consequences. Electricity, and many others.. It is an effective research and improvement tool in simulating warmth switch and modelling the temperature changer in multiphase glide structures. Ansys Fluent is a viable and famous software program that accurately integrates conjugate warmness switch. With K-Epsilon to be had, everyday wall operation mode also can be employed. This simulation provides pressure values, temperature, warmth transfer charge and velocity at numerous degrees of the annulus and pipe. Convection inside beverages (environmental and pressured), the conduction of solids, thermal radiation and the advantage of outside warmth or loss from the outer edges of the model may be automatic using Ansys Fluent. The overall performance of the parameter evaluation at the anticipated coefficient of warmth transfer fluctuations turned into accomplished primarily based on the effects of 3D on CFD simulations characterised via a vital waft course.

The principal benefits of CFD strategies are checking the thermal conductivity and hydrodynamics of the machine that make it feasible to investigate geometric adjustments (distinct feed systems such as a couple of inputs), to choose temporary working situations (fast switching time). It may be decreased at numerous prices (flexibility to trade layout parameters without hardware changes). Another high-quality benefit is that CFD provides a detailed framework for problem fixing and a higher know-how of thermal performance and hydrodynamics. This work is designed to mimic, visualize, and examine the procedures of warmth transfer and shipping in a two-pipe laboratory. This process become finished via Ansys Fluent software with CFD evaluation to degree the relationship between fluid velocity and heat switch and to visualize the fluid velocity profile and temperature profile. The major purpose of this paintings is to evaluate the performance of NTU-approach with computational fluid dynamics (CFD) simulation of a –pipe warmness exchanger primarily based on accomplishing and transmitting convection heat.

Simulation

Simulation Model

The simulation model using CFD Software is shown below:

Simulation Results

Result for Velocity Vector

Result for Velocity Profile

Result for temperature

LMTD Calculations

LMTD i.e Log Mean Temperature is calculated using the formula shown below:

LMTD Results

Simulation

Simulation is shown below

Heat Transfer Coefficient Calculations

The putting of the temperature transfer usually entails flowing fluids separated with the aid of a solid wall. The warmness is first transferred from the hot liquid to the wall by means of convection, the warmth is transferred to the wall continuously, and subsequently the warmth is transferred to the wall in bloodless and convection liquid. Any radiation effects are generally implemented to coefficients that transfer convection heat.

Overall Heat Transfer Coefficient

The most important cause in the construction of a warmness exchanger is to determine the extra location required for a certain characteristic (warmness transfer charge) the use of the available temperature distinction. The total heat transfer coefficient is the multiplication of the entire heat transfer resistance, which is the sum of a few resistances as defined earlier.

The total warmness switch coefficient of easy and dirty surfaces primarily based on the outer surface of the tube may be calculated from the following calculations,

Where,

Comments

Generally, if you work on a design you may usually come to be in a situation where your total heat transfer coefficient isn’t always within the variety of your overall heat switch coefficient. In thermal evaluation of shell and tube temperature switches you may need to have your personal warmth switch coefficient for all principal contaminants or the equivalent of the specified price. This will display that the exchanger is appropriate for heating to satisfy your needs. Having stated that, you must also ensure that the fees in query are inside applicable limits, say 30%, so as no longer to over-design the transfer.

We can commonly have an effect on facts through:

• Adjusting tube length (internal tube diameter and outer diameter tube)
• Replacing constructing substances
• Changing the connection of Nusselt. This contributes to the calculation of the coefficients that switch the warmth of the movie interior and out. We may also need to do this if we do now not have the actual values of the warmth switch coefficients and we need to calculate both.

References

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