**4.1 Computers and laptops**

*3.2.2 Boiling flow*

*Advances in Microfluidics and Nanofluids*

microchannels.

heat sink.

**166**

**4. Applications of heat sinks in real life**

parameters and working fluids.

From the cooling performance perspective, two-phase flow boiling in microchannel heat sinks is more efficient than its single-phase equivalent. A temperature lower than the critical temperature and the coolant's boiling points provide sufficient factors for increasing heat transfer rate. Due to the nature of boiling and turbulent flow in the microchannel, while requiring a low rate of coolant flow and maintaining the wall temperatures relatively uniform, the boiling heat transfer coefficient is much higher than conventional systems [107]. The main problems in this type of system are higher pressure drop and instability of the system. Due to the biphasic flow inside the channels and the creation of larger bubbles, the higher pressure drop in the system may occur because of the channels' poor design.

Numerous studies have been conducted to explore the convection heat transfer characteristics of two-phase flow boiling in micro pin-fin/channel heat sinks in recent years. Wei Wan et al. [108] experimentally examined the effect of crosssection shape on flow boiling characteristics of micro pin-fin heat sinks. Four types of staggered micro pin-fins with different cross-section shapes, i.e., square, circular, diamond, and streamline, were tested in this study. Results showed that the square shape presents the higher boiling heat transfer, followed by circular and streamlined ones. The diamond micro pin-fins presented the smallest pressure drop, while their main problem is instability at moderate to high heat fluxes. The streamline micro pin-fins presented the largest two-phase pressure drop. Besides, the square and circular micro pin-fins showed their superiority in reducing two-phase flow instabilities. Matthew Law and Poh-Seng Lee [49] conducted an experimental study of flow boiling heat transfer and pressure characteristics in straight-finned and

oblique-finned microchannels. They reported that the oblique-finned

microchannels' thermal performance is higher than straight-finned ones due to the increase in the density of bubbles generated in the convective boiling regime. The high pressure-drop in oblique-finned microchannels causes a sudden change in the flow orientation, where the fluid is being forced to flow through secondary channels. The pressure drop fluctuations in the oblique-finned pattern are much lower compared to the straight-finned; consequently, the pressure instabilities in the oblique-finned microchannels are relatively smaller than the straight-finned

Today, we can observe all levels of technological devices in everyday life, such as smartphones, gaming consoles, PCs, and laptops, etc. Companies changed many parameters to achieve the best performance of devices, including decreasing thickness, enhancing GPU and CPU numbers, and changing the appearance [109].

Based on the last researches, with the increasing number of microprocessors, the

In this section, some commercial electronic cooling systems and their operating principles are discussed. The purpose of this section is to establish a link between the scientific and commercial platforms. All effective parameters discussed in previous sections are required to fabricate optimum microchannel/micro pin-fin

heat generation is intensified; thus, heat dissipation becomes a critical issue for thermal researchers. The manufacturer's primary purpose is to achieve the best performance of devices by minimizing device and heat sink size and increasing the heat transfer rate utilizing the different items such as changing the geometrical

High-performance computing is the ability to process data and perform complex calculations at high speeds. One of the most common questions any manufacturer receives from customers is, "Why does my laptop or computer generate so much heat?" Heat is a normal byproduct of computer operation; for instance, a highperformance computer generates considerable heat than a lower performance computer. So, if the computer cannot disburse its heat, it may overheat, and device life will reduce. Therefore, this is a significant challenge for the manufacturer to solve. A heat sink is a thermally conductive device placed over a CPU or GPU to absorb some generated heat. Faster and multi-core processors require more high-efficiency heat sinks to keep their temperatures within acceptable levels. Nowadays, some companies professionally work in cooling system designing fields.

Asus [110], Alphacool [111], CoolIT Systems [112], Cool Innovations Inc. [113], Xtreme Performance Gear (XPG) [114], Coolermaster [115], Antec [116], Swiftech [117] and Thermaltake [118] are popular companies that work in cooling field. According to their operating principles, all companies used water as a cooling fluid. **Figure 6** shows some of the micro pin-fin/channel heat sinks manufactured by cooling companies.

As shown in **Figure 6a–c**, some companies use a straight pattern microchannel, and others use a pin-fin pattern (presented in **Figure 6d** and **e**). Although complex patterns increase the heat transfer rate, they cause a significant pressure drop. Some companies use different patterns without considering the pressure drop penalty, such as a micro pin-fin pattern to enhance heat sink performance.

According to Section 3.1.3, fluid and temperature MLD are decreased by using Itype flow arrangements and vertical inlet/outlet type. It concludes that the vertical inlet/outlet and I-type arrangements are implemented in commercialized products. Some of the heat sinks are made by several manufacturers and use vertical inlet/ outlet type. Asus ROG GX700 is the first liquid-cooled gaming laptop in the world and the liquid coolant is circulated around the heat-generating components like GPU by pumps. The coolant then heads back to the cooling module, where two heat sinks (radiators) help dissipate heat, that is shown in **Figure 7a**.

#### **4.2 Gaming consoles**

Many consoles were designed with cooling fans in the past, but due to advances in thermal engineering, novel consoles are designed with liquid cooling fins and heat sinks to keep the internal components safe from high generated heat. PlayStation 5 (PS5) is the new video game console developed by Sony [119] Interactive Entertainment that utilized a heat sink with a hard copper plate with

**Figure 6.** *(a) Alphacool, (b) Swiftech, (c) Thermaltake, (d) and (e) cool innovations Inc.*

aluminum dissipation fins, shown in **Figure 7b**. The generated heat from the chips was conducted into the heat sink, which used a heat pipe to move the heat across

*Effective Parameters on Increasing Efficiency of Microscale Heat Sinks and Application…*

High-performance servers are specially designed to handle large computational loads with fast data processing however, to reach higher speeds, the power dissipa-

Due to the increase in generated heat by high-performance servers, air cooling systems could not dissipate this generated heat because of their lower thermal efficiency. Therefore, new methods of cooling (i.e., liquid cooling) should be tested. Coolit system [112] is one of the companies working in the data server cooling field that utilized Coolant Distribution Unit (CDU) instead of high failure rate compo-

Wherever cooling is required, liquid cooling capabilities can be used to improve the system's thermal performance instead of traditional cooling methods. Liquid cooling systems are widely used to dissipate the heat generated by process operations in many applications, such as Aerospace systems, All-in-One devices, Food

In aerospace fields, thermal engineers have a major concern for keeping the plane at a steady temperature while avoiding ice buildup problems and protecting sensitive electronic components from extreme heat and cold. For that reason, companies should manufacture a range of heat sinks to keep planes and electronics

As shown in **Figure 7a**, an external port is required to cool down the All-in-one devices such as laptops and tablets, which may cause problems in the transportation and thermal performance of these devices. New liquid cooling methods can be used in these devices to optimize performance and facilitate transportation. It uses a small micro pump to recirculate a coolant in the integrated closed-circuit heat sink to dissipate heat away. Finally, heated liquid flows through the peltiers (Thermo-

In traditional Food Industry fields, the lineup of food processing chillers works with air-cooled systems. Air-cooled food processing chillers use ambient air to dissipate heat from food cooling processes, which have low efficiency. New liquid cooling systems chillers use water from an external cooling tower to remove heat from food processes. These systems are long-lasting, quiet, and feature energyefficiency properties. These cooling devices are best suited for medium temperature food processes, such as cheese, meat, and sauce production; potable liquid cooling systems tend to be economical solutions that deliver excellent cooling

In biological fields, cooling devices are a common tool used in research labs. A thermal cycler (also known as a PCR device) is a laboratory instrument that facilitates DNA amplification through the polymerase chain reaction. PCR

typically requires 20 to 35 cycles comprising two to three temperature steps. In the past, air-coolers used to control the heating and cooling process; by developing in the thermal engineering field, liquid cooling methods can be involved in thermal cycling to optimize the thermal efficiency and increase the number of tests per

tion of high-performance CPUs was challenging [112].

*DOI: http://dx.doi.org/10.5772/intechopen.96467*

nents such as internal pumps to circulate coolant, see in **Figure 7c**.

the fins.

**4.3 Data server**

**4.4 Other applications**

efficiency.

unit time [120].

**169**

Industry instruments, and Biology fields.

components at optimal performance.

electric modules) to cool down and return to the circuit.

*Effective Parameters on Increasing Efficiency of Microscale Heat Sinks and Application… DOI: http://dx.doi.org/10.5772/intechopen.96467*

aluminum dissipation fins, shown in **Figure 7b**. The generated heat from the chips was conducted into the heat sink, which used a heat pipe to move the heat across the fins.

#### **4.3 Data server**

High-performance servers are specially designed to handle large computational loads with fast data processing however, to reach higher speeds, the power dissipation of high-performance CPUs was challenging [112].

Due to the increase in generated heat by high-performance servers, air cooling systems could not dissipate this generated heat because of their lower thermal efficiency. Therefore, new methods of cooling (i.e., liquid cooling) should be tested. Coolit system [112] is one of the companies working in the data server cooling field that utilized Coolant Distribution Unit (CDU) instead of high failure rate components such as internal pumps to circulate coolant, see in **Figure 7c**.
