# Ultrasonic Vibration Technology to Improve the Thermal Performance of CPU Water-Cooling Systems: Experimental Investigation

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

^{2}, respectively (Figure 1). In addition, if we follow the trend related to the data in Figure 1, the maximum power consumption and heat flux values in 2022 would be achieved. However, today, the heat flux generation of many high-performance electronic devices is much higher than the roadmap predictions. On the other hand, reports state that many electronic industries are facing the challenge of eliminating very high heat fluxes to keep the operating temperature below the allowable limit (85°) [2].

## 2. Ultrasonic Wave Propagation Phenomena

## 3. Experimental Apparatus

_{w}) and the bulk temperature of the fluid flow inside the radiator tube was calculated by one of the following two methods. The mean temperature method was calculated as follows [32,33]:

_{p}represents the specific heat capacity. The fluid temperatures at the inlet and outlet of the radiator tube are indicated by T

_{i}and T

_{o}, respectively. In addition, the dimensionless Nusselt number for the flow inside the radiator tube is as follows:

## 4. Uncertainty Analysis

## 5. Result and Discussion

^{6}and 0.5 ≤ Pr ≤ 2000, was used to validate the present results:

_{up}/q

_{0}) with different values of the fan speed and ultrasonic power (UP) levels. Regarding this figure, the effects of ultrasonic vibrations were highlighted with lower fan speeds and higher ultrasonic power levels. The graphs show that the most significant increase in the heat transfer ratio of 1.18 occurred at a power level of 120 W and a fan speed of 880 rpm.

## 6. Conclusions

_{up}/q

_{0}) and Nusselt number ratio (Nu

_{up}/Nu

_{0}) were 1.18 and 1.24, respectively. The technology of continuously applying ultrasonic vibrations, along with the advantage of increasing heat transfer, can pave the way for the practical use of nanofluids in computer cooling systems due to their anti-fouling and anti-agglomeration properties.

## Author Contributions

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

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**Figure 1.**Prediction of maximum heat flux and power of microprocessor chips [1]. Predictions show that the rate of heat flux generation in microprocessors is increasing rapidly.

**Figure 2.**Schematic of laboratory equipment. 1: Temperature sensor; 2: cooling fan; 3: airflow meter; 4: ultrasonic generator; 5: ultrasonic transducer; 6: radiator; 7: water tubes; 8: computer processor; 9: control unit; 10: laptop.

**Figure 4.**Comparison of the results obtained from the average temperature and LMTD methods with the values obtained from the Gnielinski correlation [35]. The Reynolds and Prandtl numbers were 3265 and 6.46, respectively. Comparing the results showed that both methods used in the present work, i.e., the average temperature method and the LMTD method, had acceptable accuracy.

**Figure 5.**The outlet temperature reduction percentage with different fan speeds and ultrasonic power levels. The outlet temperature was decreased by increasing the ultrasonic power level. The ultrasonic effects were highlighted at lower fan speeds. The maximum error of the data in this figure is ±1.9%. The green, blue, and red colors of the columns are related to ultrasonic power levels of 30, 60, and 120 Watts.

**Figure 6.**Changes in the heat flux ratio with different fan speeds and ultrasonic power levels. The positive effects of ultrasonic vibrations on heat transfer enhancement increased by increasing the ultrasonic power level and decreasing the fan speed. The maximum error of the data in this figure is ±2.1%. The green, blue, and red colors of the columns are related to ultrasonic power levels of 30, 60, and 120 Watts.

**Figure 7.**Changes in the convection coefficient ratio with different values of ultrasonic power levels and fan speeds (FS) obtained by (

**a**) the mean temperature and (

**b**) LMTD methods. Applying ultrasonic vibrations increased the convection coefficient ratio, especially at lower fan speeds and higher ultrasonic powers. The maximum error of the data in this figure is ±2.3%.

**Figure 8.**Changes in the Nusselt number ratio according to the cooling airflow rate at different ultrasonic power levels (UP). The Nusselt number ratio decreased by increasing the cooling airflow rate. Variation in the Nusselt number ratio was a linear function of the cooling airflow rate.

Parameter | Uncertainty |
---|---|

Heat transfer rate | ±2.1% |

Heat transfer coefficient | ±2.3% |

Nusselt number | ±2.4% |

**Table 2.**Absolute values of outlet temperature difference in different ultrasonic power levels and fan speeds.

Ultrasonic Power Level | Fan Speed (RPM) | Outlet Temperature (°C) |
---|---|---|

UP = 0 | 70 | 21.20 |

105 | 20.91 | |

140 | 20.37 | |

175 | 20.21 | |

UP = 30 W | 70 | 20.74 |

105 | 20.49 | |

140 | 20.01 | |

175 | 19.95 | |

UP = 60 W | 70 | 20.68 |

105 | 20.41 | |

140 | 19.89 | |

175 | 19.82 | |

UP = 120 W | 70 | 20.51 |

105 | 20.29 | |

140 | 19.84 | |

175 | 19.77 |

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**MDPI and ACS Style**

Amiri Delouei, A.; Sajjadi, H.; Ahmadi, G.
Ultrasonic Vibration Technology to Improve the Thermal Performance of CPU Water-Cooling Systems: Experimental Investigation. *Water* **2022**, *14*, 4000.
https://doi.org/10.3390/w14244000

**AMA Style**

Amiri Delouei A, Sajjadi H, Ahmadi G.
Ultrasonic Vibration Technology to Improve the Thermal Performance of CPU Water-Cooling Systems: Experimental Investigation. *Water*. 2022; 14(24):4000.
https://doi.org/10.3390/w14244000

**Chicago/Turabian Style**

Amiri Delouei, Amin, Hasan Sajjadi, and Goodarz Ahmadi.
2022. "Ultrasonic Vibration Technology to Improve the Thermal Performance of CPU Water-Cooling Systems: Experimental Investigation" *Water* 14, no. 24: 4000.
https://doi.org/10.3390/w14244000