**1. Introduction**

Liquid cooling in microchannels is a highly successful method of removing excess heat from the circuits, with water being the most common heat transfer fluid on the desktop. The important advantage of using water cooling over air cooling is due to enhanced thermal properties of water (higher thermal conductivity and heat capacity property).

The noteworthy development of power densities in the Central Processing Unit (CPU) chips and also the reduction of their surface area contribute to the production of high heat flux. Computers and the processor's thermal management and its operation without overheating are a difficult task nowadays. The increase of transistors used in the circuit has reached up to 580 million. Microelectronics devices are safe on their operating temperature for the range of 70–80 °C and the reliability is decreased 5% for every degree rise in temperature. One sensible manner is to

use liquid fluid to gain the generated heat by convective means and deliver it to the external surroundings. Also, convective systems have the potential to be designed for various configurations. As proved in [1], bulk heat transfer is more significant than the thermal properties for most applications because bulk transport is the main reason for heating or cooling. This micron-sized particle, when used in low volume fractions prevents particles clogging and also reduces the pressure drop.

PC coolers are helpful for this reason using appropriate working liquids coolant. They will greatly enhance the system's cooling performance. Heat sinks are equipped for simultaneous cooling of several chips and also processor supply circuits, graphic cards, and CPU. In employing a heat sink very low flow rates of coolants are required and thereby the noise generations are also minimal as mentioned in [2].

This liquid cooling is categorized into active and passive cooling. The principle of an active liquid cooling system for computers is the same as that used in combustion engines, with the coolant being water which is circulated by a pump. This Heat sink made of microchannels is mounted on the CPU and sometimes on the components like GPU and Northbridge and cooled typically a radiator. The radiator itself is cooled externally by employing a fan [3].

Both active liquid cooling systems and passive liquid cooling systems are used depending upon the requirements. The passive system often discards a fan or a water pump, hence the reliability of the system can be theoretically increased and or making it quieter than active systems. However, they are much less efficient in discarding the heat and thus also need to have much more coolant and thus a much bigger coolant reservoir (giving more time to the coolant to cool down).

Although liquid cooling under forced convection enables higher heat dissipation rates, air cooling is the most common technique for heat removal. The primary advantage of air cooling is its easy operability with less noise. Forced air-cooling processes may be further classified into serial and parallel flow systems. In a serial system, the air stream is passed over successive rows of modules or boards, so that each row is treated by the same air that has been preheated by the previous row. The power and airflow requirements are the key factors in serial airflow resulting in an extensive air temperature rise across the machine. Parallel airflow systems can be used to reduce the temperature rise in the cooling air. In this system, the printed circuits or modules are all equipped with a parallel air supply. In this method, each board or module is supplied with a fresh supply of cooling air [4].
