/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 74 Consider a heat sink with optimu... [FREE SOLUTION] | 91影视

91影视

Log out

Learning Materials

Features

Discover

Chapter 9: Problem 74

Consider a heat sink with optimum fin spacing. Explain how heat transfer from this heat sink will be affected by (a) removing some of the fins on the heat sink and (b) doubling the number of fins on the heat sink by reducing the fin spacing. The base area of the heat sink remains unchanged at all times.

Short Answer

Expert verified
Answer: Removing some fins from the optimal heat sink will decrease heat transfer capacity due to a reduced surface area available for heat transfer. Doubling the number of fins with reduced fin spacing will not necessarily result in a linear increase in heat transfer, as the restricted airflow may reduce convection.

Step by step solution

01

Understanding how heat is transferred in a heat sink

Heat sinks work by transferring heat from a high temperature source, such as a microprocessor or an electronic device, to the air surrounding it. The heat transfer occurs primarily through conduction and convection. Conduction occurs through the fins and base material of the heat sink, while convection takes place between the fins and the surrounding air. The goal of the heat sink is to maximize heat transfer to improve cooling performance.
02

Discuss the role of fins in a heat sink

Fins in a heat sink increase the surface area available for heat transfer, which enhances convection. An optimal fin spacing allows for a balance between heat conduction and heat dissipation through convection. If the fins are too close together, the air flow between them is restricted, which reduces convection. If the fins are too far apart, the overall surface area available for heat transfer is reduced.
03

Assess the effect of removing fins on heat transfer

When some fins are removed from the optimal heat sink, the fin spacing becomes greater than optimal. As a result, there is a decrease in the overall surface area available for heat transfer. This reduction weakens the conduction and convection in the heat sink. Consequently, heat transfer from the heat sink decreases.
04

Assess the effect of doubling the number of fins and reducing fin spacing on heat transfer

When the number of fins is doubled and the fin spacing is reduced, the overall surface area available for heat transfer increases. However, the reduced fin spacing may inhibit the flow of air between the fins, reducing the rate of convection. The net effect on heat transfer will depend on the relative balance between the improved conduction due to the increased surface area and the reduced convection due to restricted airflow. In conclusion, removing fins from the optimum heat sink reduces the heat transfer capacity due to decreased surfaces area available for heat transfer, while doubling the number of fins with reduced fin spacing may not necessarily show a linear increase in heat transfer as the convection may be reduced due to the restricted airflow.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Fin Spacing
In a heat sink, fin spacing plays a pivotal role in determining its efficiency at heat transfer. The fins are structures that stick out from the base of the heat sink, and their spacing impacts how heat is absorbed and dissipated.

When there's optimal fin spacing, the heat sink can effectively use conduction through its base and fins and convection via air moving between the fins.
  • Too close spacing: Restricts airflow, lowers convection efficiency.
  • Too wide spacing: Reduces surface area for heat transfer, hindering conduction and convection both.
By manipulating fin spacing intelligently, engineers can enhance the heat sink's capacity to handle heat, ensuring the components remain cool and operational.
Convection
Convection refers to the movement of heat through fluids such as air or water. In the context of a heat sink, convection is the process by which heat is transferred from the sink's surface into the surrounding air.

For effective convective heat transfer, optimal airflow between the fins is crucial.
  • Large gaps allow smooth air movement, promoting cooling.
  • Tight gaps may cause airflow blockages, reducing cooling potential.
Balancing the fin arrangement to create a steady airflow ensures the heat sink can effectively disperse heat away, preventing overheating of the device it's attached to.
Conduction
Conduction is the process where heat transfers through materials without the movement of the material itself. In a heat sink, conduction occurs primarily within the metal fins and base material.

It allows heat from the electronic component to spread throughout the heat sink.
  • Materials like aluminum or copper are often used as they're excellent conductors.
  • Efficient conduction helps distribute heat evenly across the heat sink.
Understanding how conduction works helps in designing heat sinks that maximize heat distribution before it becomes dissipated by convection.
Heat Transfer
The overall goal of using a heat sink is to efficiently remove heat from a system. Heat transfer in a heat sink involves the synergy of conduction and convection.

Two main factors help enhance heat transfer:
  • Increasing the surface area (more fins can help).
  • Ensuring efficient airflow (proper fin spacing aids this).
Ultimately, heat transfer efficiency depends on maintaining a balance between sufficient surface area for conduction and adequate spacing to allow effective convection. Understanding these interactions is key for optimizing a heat sink's performance to prevent system overheating.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Consider a double-pane window whose air space is flashed and filled with argon gas. How will replacing the air in the gap by argon affect ( \(a\) ) convection and ( \(b\) ) radiation heat transfer through the window?

Consider a fluid whose volume does not change with temperature at constant pressure. What can you say about natural convection heat transfer in this medium?

The components of an electronic system dissipating \(180 \mathrm{~W}\) are located in a 4-ft-long horizontal duct whose cross section is 6 in \(\times 6\) in. The components in the duct are cooled by forced air, which enters at \(85^{\circ} \mathrm{F}\) at a rate of \(22 \mathrm{cfm}\) and leaves at \(100^{\circ} \mathrm{F}\). The surfaces of the sheet metal duct are not painted, and thus radiation heat transfer from the outer surfaces is negligible. If the ambient air temperature is \(80^{\circ} \mathrm{F}\), determine (a) the heat transfer from the outer surfaces of the duct to the ambient air by natural convection and \((b)\) the average temperature of the duct. Evaluate air properties at a film temperature of \(100^{\circ} \mathrm{F}\) and 1 atm pressure. Is this a good assumption?

A \(1.5\)-m-diameter, 4-m-long cylindrical propane tank is initially filled with liquid propane, whose density is \(581 \mathrm{~kg} / \mathrm{m}^{3}\). The tank is exposed to the ambient air at \(25^{\circ} \mathrm{C}\) in calm weather. The outer surface of the tank is polished so that the radiation heat transfer is negligible. Now a crack develops at the top of the tank, and the pressure inside drops to \(1 \mathrm{~atm}\) while the temperature drops to \(-42^{\circ} \mathrm{C}\), which is the boiling temperature of propane at \(1 \mathrm{~atm}\). The heat of vaporization of propane at \(1 \mathrm{~atm}\) is \(425 \mathrm{~kJ} / \mathrm{kg}\). The propane is slowly vaporized as a result of the heat transfer from the ambient air into the tank, and the propane vapor escapes the tank at \(-42^{\circ} \mathrm{C}\) through the crack. Assuming the propane tank to be at about the same temperature as the propane inside at all times, determine how long it will take for the tank to empty if it is not insulated.

In an ordinary double-pane window, about half of the heat transfer is by radiation. Describe a practical way of reducing the radiation component of heat transfer.
See all solutions

Recommended explanations on Physics Textbooks

Turning Points in Physics

Read Explanation

Engineering Physics

Read Explanation

Magnetism and Electromagnetic Induction

Read Explanation

Classical Mechanics

Read Explanation

Linear Momentum

Read Explanation

Further Mechanics and Thermal Physics

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.