VISHWAKARMA INSTITUTE OF TECHNOLOGY, PUNE – 411037

Subject: Heat Transfer

Home Assignment: Methods of cooling electronic components

Group No: 1 Batch: D1

Group Members:

1. SAHIL BHAT (01)

2. AKASH SALUNKHE (03)

3. MANDAR SALVI (04)

4. SAMEET SHAIKH (05)

5. DHIRAJ SOLUNKHE (22)

Guide: Prof. Dr. SUNIL SHINDE

Practically every element of modern life now includes electronic devices, from high-powered computers to toys and appliances. The temperature control of components inside an electronic system is referred to as electronics cooling. Power density has dramatically increased as a result of the recent surge in electronics and their ongoing use.

Because electronic components require the flow of electric current to function, they are vulnerable to overheating because this is a side effect of current flow over a resistance. The quantity of heat produced per unit volume has dramatically increased as a result of the continued shrinking of electronic equipment. With temperature, the failure rate of electronic equipment rises exponentially. Consequently, thermal control has evolved.

How Does Heat Impact Electronic Components?

All electronic parts release heat to a certain level. What degree of heat do these parts reach, and how does it effect the final product? Thermal management is an important consideration in design, as it may lead to overheated goods and expensive recalls.

If we are employing components that dissipate a lot of heat, selecting the proper thermal management strategy is crucial. For instance, frequent overheating causes include FGPAs, graphic processors, power transistors, voltage regulators, and high-power LEDs. Compared to their less power-hungry competitors, these components frequently generate greater heat. Such elements can cause a design to become extremely heated. It is common for components, such microprocessors, to reach 100°C. Thankfully, we can estimate how hot a component will get by referring to the thermal coefficient chart in its datasheet.

Cooling methods based on heat transfer:

The need to reduce cooling system costs and the strategy to increase heat-transfer efficacy provide a substantial challenge with each new product that enters the market. Their normal performance and lifetime might decline more quickly than anticipated if they are not sufficiently cooled. Additionally, as operational temperatures rise, electronic equipment failure rates rise as well. Based on the efficiency of heat transport, solutions have been developed to deal with them. The traditional cooling modes can be classified into four general categories which are:

Natural convection air cooling
Forced convection air cooling
Liquid cooling
Phase change material

1. Natural convection air cooling:

When there isn't any forced air movement coming from a fan, blower, or any other source, the condition is said to be cooling by natural convection. Under natural convection cooling, heat from the heat source causes the air inside the heat sink's fins to warm up. Because it is less dense and has a greater temperature, the air rises out of the heat sink. The heat sink will be cooled by the modest quantity of airflow created by this movement within the heat sink fins. Refrigerator cooling, water heating, and appliance cooling are examples of natural convective heat transfer.

2. Forced convection air cooling:

Convection under force In the process of extracting or transferring heat from or to objects at temperatures other than the flow temperatures, fluid flow produced by external means, such as a fan or an externally imposed pressure gradient, is referred to as heat transfer. The speed of the air has an impact on the rate of heat transmission. The rate of heat transmission increases with air velocity. Convective heat transfer and flow motion are both components of forced convection. Common uses of forced convection include cooling electronic components with fans, heating exchangers, cooling laptops or computers with fans, cooling fluids in automobiles with externally forced air, etc.

3. Liquid cooling:

• Liquid cooling is the decrease of warm in electronic and mechanical gadgets through abusing the properties of fluids. Fluid cooling may be a solidly built up cooling strategy in numerous current innovations. Automobiles, centralized computers and the frameworks of computer devotees have utilized water cooling for numerous a long time. The strategies and coolants can vary between and inside these categories. • Liquid cooling has higher warm exchange proficiency than discuss cooling and is utilized in high-power modules. The two sorts of glycol most commonly utilized for fluid cooling applications are ethylene glycol and water (EGW) and propylene glycol and water (PGW) solutions.

4. Phase change Material:

• A stage alter fabric (PCM) may be a substance which releases/absorbs adequate vitality at stage move to supply valuable heat or cooling. For the most part the move will be from one of the primary two crucial states of matter - strong and fluid - to the other. By dissolving and setting at the stage alter temperature (PCT), a PCM is able of putting away and discharging expansive sums of vitality compared to sensible warm storage.

• Heat is retained or discharged when the fabric changes from strong to fluid and bad habit versa or when the inside structure of the fabric changes; PCMs are in like manner alluded to as inactive warm capacity (LHS) materials. The foremost cost-effective stage-alter fabric (PCM) for vitality capacity is the paraffin wax.

All electronic gadgets and circuits create over the top warm whereas working. The warming up of the electronic components needs legitimate warm vitality direction. This is to make strides the unwavering quality and guarantee the smooth working of the electronic machine. In brief, the most reason of an electronic cooling framework is to permit your machine to work at faster-operating speeds. It is as straightforward as overseeing the sum of warm yield to coordinate it with the control input without any undesirable vitality interactions. There are a few procedures for cooling, and a few of the foremost well-known ones incorporate warm sinks, thermoelectric coolers, constrained discuss frameworks, fans, warm channels, and others.

Other general popular cooling techniques are:

1.Heatsink:

Heatsinks are commonly used for components like power transistors and microprocessors. They feature fin-like surfaces, which maximize the heat transfer to the air. Often, the heat transfer compound is applied between the component and heatsink to improve heat conduction efficiency.

2.Heat Pipes:

Heat pipes are cylindrical copper pipes used to transfer heat away from high-temperature components. Sometimes, heat pipes may contain liquids, such as water, to remove heat via a condenser. One recent innovation is miniature heat pipes, which conduct heat more efficiently and are small enough to be embedded into a PCB.

3.Thermoelectric Cooler:

Thermoelectric cooling uses the Peltier effect to create a heat flux at the junction of two different types of materials. A Peltier cooler or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other, with consumption of electrical energy, depending on the direction of the current.

Such an instrument is also called a Peltier device, thermoelectric cooler (TEC). It can be used either for heating or for cooling. It can also be used as a temperature controller that either heats or cools.

Recent advancements:

1.New thermal management technology for electronic devices reduces bulk while improving cooling:

A team from UIUC and UC Berkeley have published a paper in Nature Electronics detailing a new cooling method that offers a host of benefits, not the least of which is space efficiency that offers a substantial increase over conventional approaches in devices' power per unit volume. Gebrael- A device using the new solution is dramatically smaller than one using heat sinks, which are bulky. "And this translates to much higher power per unit volume. We were able to demonstrate a 740% increase in the power per unit volume." They will also implement the coatings on full-scale power modules and GPU cards, whereas they used only simple test boards in the initial work.

2.NANO FLUIDS FOR HEAT PIPES:

Heat pipes are used to transfer a lot of heat from one component to another. Nano fluids are being included in heat pipes to accelerate heat transfer from one point to another without impacting in-rate temperatures. Mercury/sodium in the temperature range of 500-15000C to cryogenic fluid employing Helium and Nitrogen for a few Kelvin temperatures are some of the fluids utilised in heat pipes. The development of nano fluids, or fluids that combine a traditional heat transfer base with nanometer-sized oxide or metallic particles suspended in the liquid, has recently been claimed to result in significant improvements in heat transfer rates. By dispersing copper, alumina-silver suspended in water, Li et al demonstrated considerable improvements in heat transfer characteristics of heat pipes in their trials. By distributing roughly 0.1 percent micro particles, these systems increased heat conductivity by more than 20- 30 percent. Such trials have sparked interest in using nano fluid-based heat pipes as part of a thermal management system for satellite applications. Because of these benefits, the fluid with ultra fine suspended nano particles will be the advanced fluid for satellite heat pipe applications. Oil-free operation, smaller dimensions, decreased weight, and minimal power usage are all advantages of improved heat transmission. For the high heat flux encountered during ascent and reentry of the space vehicle, NASA has established a road map for the development of high temperature heat pipes with nano fluids.

3.MICRO HEAT PIPES

High thermal cavities have formed in different circuits for diverse applications as a result of the development of high density electronic fabrications and new control devices. These isolated regions are hotspots for high-density thermal dissipation, which has an impact on nearby components and circuits. It's even more problematic in space, where convective heat transmission is essentially non-existent due to the lack of an environment. Several components of the study are covered, including package design, thermal interface, low thermal resistance materials, heat sinks, and cooling systems. Micro heat pipes are now thought to be the most effective technique to distribute these heats due to their low thermal resistance. Several scholars have proposed a range of micro heat pipe development methodologies. One of the most popular designs is a micro heat pipe made of silicon wafers with copper plated channels. It provides a high level of wetting of the surfaces to facilitate liquid flow. The wick drying problem in these heat pipes prevents the fluid from returning from the condenser to the evaporator portion. A unique design is used to moisten the wick and establish liquid flow back by introducing side channels known as arteries. These arteries have a smaller cross area than the main heat pipes, but they maintain a steady, uninterrupted flow of fluid for operation without any power.

4.HYBRID TWO PHASE LOOP TECHNOLOGY:

Thermal controls in heat pipes are controlled using two-phase cooling methods utilised on satellites. Loop heat pipes (LHP) and capillary pumped loops are examples of these devices (CPL). They are a passive system with a high level of reliability. However, in terms of thermal fluxes, transport distances, and various heat source capabilities, these passive devices are unable to match the thermal demands today required in satellites. Mechanical pumps were successfully used by NASA's Mars Exploration Rover to reject heat. However, due to high pumping pressure, flow instability in the micro-channel, complex fluid reconditioning, and nozzle clogging/erosion, the system has low reliability. It has reduced the value of such an active system for space applications significantly. For satellite applications, a hybrid system combining pump-assisted two-phase cooling with heat pipes has recently gained appeal. A tiny active mechanical pumping system is combined with a passive capillary pumping heat pipe in Hybrid Two- Phase Loop (HTPL) technology. Evaporators, a condenser, a liquid reservoir, and a mechanical pump make up such a system. The evaporator is the system's heart, where heat must be absorbed. It has a fluid connection on the input side, an excess liquid exit, and a vapour outlet on the other side. The capillary structure of the evaporator distributes the liquid while separating the vapour from the excess liquid. Regardless of the heat input, it delivers the finest boiling condition. Adding more than one evaporator, which removes heat from many sources, allows the technique to be improved further. The hybrid two-phase loop has exhibited a reliable operation system, small cooling systems with a wide range of design freedom, and substantial heat transfer. It can be used for a range of spacecraft in zero-gravity environments.