EKC 394 Chemical Engineering Laboratory II: Coil Heat Exchanger Experiment

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Questions and Answers

What is the main objective of determining the individual film coefficients hi and ho and overall heat transfer coefficient Uo?

To evaluate the pressure drop across the coil heat exchanger

To determine the effect of hot water temperature on hi and ho and overall heat transfer coefficient Uo

To assess the flow rate of hot and cold water

To measure the heat transfer efficiency of the coil heat exchanger (correct)

How does the crisscross or helical pattern in the coil heat exchangers contribute to their efficiency?

It produces laminar flow which enhances heat transfer

It creates a swift uniform heating of fluids increasing the total heat transfer coefficient (correct)

It creates a significant heat transfer surface within a heavy compact shell

It reduces the total heat transfer coefficient

In what way does the design of corrugated tubes contribute to the efficiency of coil heat exchangers?

It produces a turbulent flow where the desired feature of fluctuating velocities is achieved (correct)

It decreases the heat transfer surface area

It increases deposit buildup in the tubes

It reduces the turbulence in fluid flow

What is the purpose of having a large number of closely packed tubes in coil heat exchangers?

To increase the total heat transfer coefficient Signup and view all the answers

How does the connection locations and angle of entry contribute to the efficiency of coil heat exchangers?

They reduce deposit buildup by performing a 'scoop and lift' action Signup and view all the answers

What is the purpose of using circular layers of helically corrugated tubes inside coil heat exchangers?

To produce a significant heat transfer surface within a light compact shell Signup and view all the answers

What is the purpose of determining the individual film coefficients hi and ho?

To analyze the efficiency of the overall heat transfer Signup and view all the answers

How does the Dittus-Boelter equation contribute to the determination of heat transfer coefficient?

By relating Nusselt number to Reynolds and Prandtl numbers Signup and view all the answers

What is the significance of checking that the flow is turbulent before using the Dittus-Boelter equation?

To verify that the flow conditions satisfy the equation's assumptions Signup and view all the answers

How does adjusting valve V4 or V5 impact the hot water flow rate?

It increases the hot water flow rate Signup and view all the answers

Why is it necessary to repeat the experiments for different cold water flow rates?

To observe how cold water flow rate affects heat transfer efficiency Signup and view all the answers

What does 'Allow the temperature to reach steady state' help in achieving during the experiment?

Minimization of temperature fluctuations for precise data collection Signup and view all the answers

How does estimating Uo from the actual rate of heat transferred to cold water contribute to the experimentation process?

It provides a measure of overall energy efficiency in heat transfer Signup and view all the answers

What is the role of reading and recording temperatures TC1, TC2, TH1, and TH2 every 10 minutes until they reach steady state?

To monitor and analyze temperature changes during steady state conditions Signup and view all the answers

What is the purpose of filling the cold and hot tanks with water at the beginning of the procedure?

To create an isolated system for accurate heat transfer measurements Signup and view all the answers

How does estimating shell side film coefficient ho contribute to understanding heat exchanger performance?

It allows comparison with theoretical values to assess heat exchanger effectiveness Signup and view all the answers

Study Notes

Objective of Heat Transfer Coefficients

Determining individual film coefficients (hi and ho) and overall heat transfer coefficient (Uo) is essential for analyzing efficiency in heat exchangers.
Individual coefficients help in understanding the heat transfer rates between both fluids and the heat exchange surface.

Efficiency of Crisscross or Helical Patterns

Crisscross or helical patterns in coil heat exchangers enhance turbulence, promoting better mixing and heat transfer.
These designs reduce boundary layer thickness, allowing for improved thermal performance.

Contribution of Corrugated Tubes

Corrugated tubes increase turbulence and disrupt laminar flow, which boosts heat transfer efficiency.
The design provides a larger surface area for heat transfer compared to smooth tubes.

Role of Closely Packed Tubes

A large number of closely packed tubes maximizes surface area for heat exchange, improving overall heat transfer rates.
This configuration helps in efficient fluid distribution and heat transfer between fluids.

Impact of Connection Locations and Angle of Entry

The design and positioning of connection locations and angles affect flow patterns, leading to improved mixing and thermal performance in heat exchangers.
Proper angles decrease dead zones and enhance fluid dynamics within the system.

Purpose of Circular Layers of Helically Corrugated Tubes

Circular layers enhance flow distribution and provide uniform heat transfer characteristics.
They help maintain the efficiency of the heat exchanger by preventing stagnant zones.

Importance of Determining Film Coefficients

Understanding hi and ho enables engineers to tailor heat exchangers for specific applications, optimizing heating or cooling processes.
Coefficients are critical for calculating overall heat transfer efficiency.

Contribution of the Dittus-Boelter Equation

The Dittus-Boelter equation provides a means to calculate heat transfer coefficients under turbulent flow conditions.
It enables engineers to estimate performance based on fluid properties and flow rates.

Significance of Turbulent Flow Check

Confirming turbulent flow is crucial because the Dittus-Boelter equation is only applicable for such conditions, ensuring reliable results.
Turbulent flow promotes better mixing and enhances heat transfer effectiveness.

Impact of Adjusting Valves V4 and V5

Adjusting valve settings alters the hot water flow rate, allowing for optimization of heat transfer processes according to operational needs.
Balancing flow rates can help achieve desired temperature outcomes in the system.

Necessity of Varying Cold Water Flow Rates

Repeating experiments with different cold water flow rates allows for comprehensive analysis of performance under varying conditions.
This practice helps in identifying optimal operational parameters for heat exchange efficiency.

Importance of Achieving Steady State

Allowing temperature to reach a steady state ensures consistent thermal readings, which are necessary for accurate data analysis.
This condition indicates that the system has stabilized, making measurements reliable.

Role of Uo Estimation

Estimating overall heat transfer coefficient (Uo) from the actual heat transfer rate aids in evaluating the efficiency of the heat exchanger.
This estimation allows for practical assessments and adjustments during experimentation.

Function of Temperature Recording

Recording temperatures (TC1, TC2, TH1, TH2) systematically provides data to track performance and verify steady state achievement.
Continuous monitoring aids in the analysis of thermal performance over time.

Purpose of Filling Tanks with Water

Filling cold and hot tanks with water is crucial to initiating the heat exchange process and establishing baseline conditions.
This step ensures that both fluids are available for effective heat transfer during experimentation.

Contribution of Estimating Shell Side Film Coefficient (ho)

Estimating the shell side film coefficient (ho) is vital for understanding the thermal resistance and performance of the heat exchanger.
Accurate estimates help in diagnosing issues and optimizing design for better efficiency.

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Description

This quiz covers the objectives and introduction of the Coil Heat Exchanger experiment in the Chemical Engineering Laboratory II course at Universiti Sains Malaysia. It includes topics such as determining individual film coefficients, overall heat transfer coefficient, and the effects of water flow rate and temperature on heat transfer.