Katsuhiro Koizumi

Relationships Between Supply Flow Rate of Small Cooling Fans and Pressure Drop Characteristics in Electronic Enclosure

This study describes a prediction method of a supply flow rate of axial cooling fans mounted in high-density packaging electronic equipment. The performance of an air-cooling fan is defined by its P – Q (pressure difference – flow rate) curve. Generally the operating point of a fan, which is the operating pressure and the flow rate in equipment, is the point of intersection of a P – Q curve and a flow resistance curve. Recently, some researchers reported that catalogue P – Q curves have not necessarily been able to predict a correct supply flow rate in thermal design of high-density packaging equipment. Our study aims to improve prediction accuracy of the supply flow rate. In this report, a relationship between the P – Q curve and a pressure drop characteristic in a fan-mounted enclosure was investigated. A test enclosure which includes an obstruction was mounted in front of a test fan and the supply flow rate of the fan was measured while changing the obstruction. Additionally the flow resistance curves in the test enclosure were measured and the relationship among the supply flow rate, the P – Q curve and the flow resistance curve was investigated. It is found that the correct supply flow rate can be obtained by using the flow resistance from the enclosure inlet through the fan outlet and the revised P – Q curve which is made compensation for the pressure drop at the inlet and the outlet of the fan.Copyright

Application of Thermal Network Model to Transient Thermal Analysis of Power Electronic Package Substrate

In recent years, there is a growing demand to have smaller and lighter electronic circuits which have greater complexity, multifunctionality, and reliability. High-density multichip packaging technology has been used in order to meet these requirements. The higher the density scale is, the larger the power dissipation per unit area becomes. Therefore, in the designing process, it has become very important to carry out the thermal analysis. However, the heat transport model in multichip modules is very complex, and its treatment is tedious and time consuming. This paper describes an application of the thermal network method to the transient thermal analysis of multichip modules and proposes a simple model for the thermal analysis of multichip modules as a preliminary thermal design tool. On the basis of the result of transient thermal analysis, the validity of the thermal network method and the simple thermal analysis model is confirmed.

Thermal Analysis of Natural Convection Cooled Switch Mode Power Supplies

This paper describes an application example of thermal flow simulation to the design of a switch mode power supply (SMPS) that is natural convection air-cooled. In this analysis, the modeling of printed circuit board (PCB) and power semiconductor devices was examined using the design of experiments method. The PCB was treated as a simple plate, and average thermal conductivity was not considered. The power semiconductor devices were modeled as a simple hexahedral resistive network block. As the heat generation sources, a field effect transistor (FET) and a diode were considered in the simulation, and the calculation method of power loss is described. The difference between measured and calculated values for power semiconductor devices was found to be within approximately 10 K.Copyright

Thermal characterization of high-density interconnects: A methodolgy tested on a model coupon

The high-density interconnection substrate invariably poses enormous difficulty to thermal design analysts due to complex metal layout patterns embedded in the dielectric matrix. A modeling method is proposed, which produces effective thermal conductivity values for elements of the substrate under a specified boundary condition.

CFD Simulation of Wave Soldering Process (Case of Simple 2-Dimensional Configurations)

Wave soldering process with a simple model has been studied numerically. Wave soldering process is one of major soldering process used in the manufacture of electronics. The purpose of this study is to clarify how a lifting velocity and an arrangement of parts affect the solder volume on the joint after wave soldering process. Open source computational fluid dynamics software, OpenFOAM, is used. Solder is assumed to be kept at the constant temperature over the melting point. Flow of melting solder and surrounding air is simulated and the dynamic movement of the interface between two fluids is captured using VOF method. Two dimensional arrangements of the parts were adopted. The dynamic movement of the solder surface is visualized from numerical results. The size of a rear land affects the solder volume on the front parts. It is confirmed that the changes of the volume is closely related to the solder surface configuration at the moment of the detachment from the solder bath.Copyright

Study on P-Q Curves of Cooling Fans for Thermal Design of Electronic Equipment (Effects of Opening Position of Obstructions Near a Fan)

This study describes an operation pressure and supplies flow rate of an axial cooling fan installed in high-density packaging electronic equipment. Fan performance is generally defined by their P-Q curve, specifically, a relationship between fan pressure rise (ΔP) and flow rate (Q). A compact cooling fan often operates in a high-density mounting device, which may decrease the fan performance. In this study, we focus on an obstruction near a fan, which is electronic components such as PCBs, capacitors and heat sinks, as one of a factor which decreases fan performance. We installed a perforated plate which simulated the above components near a fan and measured the P-Q curve. To investigate a relationship between a fan performance decrease and an opening position near the fan, a part of the perforated plate was closed. Closed position was changed and explored an opening condition which caused the dominant fan performance decrease. From experiments, it was found that the fan performance was decreased when flow passage in front of a fan was blocked by an obstruction. Especially, when flow passage in front of a fan hub was blocked, a dominantly reduction of fan pressure was caused. An obstruction rear a fan has no effect on a fan performance curve itself. In addition, opening conditions in front of a fan tip had a little influence on a fan pressure characteristic when there was no obstruction in front of a hub.Copyright

Development of a self-cooling system utilizing waste heat from electronic equipment

There is potential for the waste heat from electrical and electronic equipment to power cooling systems for the equipment itself, resulting in energy savings. We investigated the feasibility of a self-cooling mechanism, in which refrigerant in a sealed container is heated by waste heat, a turbine is rotated by the vapor generated, and the rotational force is extracted using a magnetic coupling, which in turn is used to rotate a cooling fan. In this study, a system was prototyped and performance tests carried out to characterize its performance. As a result of repeated improvement of the prototype apparatus, circulation of the refrigerant in the apparatus was confirmed. By increasing the pressure differential between the heat chamber and the refrigerant receiver using a nozzle with optimum bore size, a rotor with an inner ring inside the chamber providing a magnetic coupling to an outer magnetic ring outside the chamber was successfully rotated. The above verified the validity of the systems principle

Evaluation of pressure drop characteristics around axial cooling fans with electrical components

This paper describes the details of pressure drop characteristics around axial cooling fans mounted in high-density packaging electronic equipment in order to improve prediction accuracy of supply flow rate of the fans in thermal design. Forced air convection cooling driven by cooling fans is the commonest strategy for dissipating heat from electrical devices. Cooling performance of the fans is mainly decided by supply airflow rate. The supply flow rate is strongly affected by pressure drop characteristics in electronic equipment. Especially in the case of high-density packaging electronic equipment, the airflow around the fan generally becomes complex and an accurate prediction of pressure drop characteristics around the fans become significantly difficult. In addition, due to the change of the airflow pattern around the fans by the electrical components mounted near the fans, a deterioration of fan performance itself is sometimes caused. Hence the accurate prediction of supply flow rate of the fans in high-density packaging electronic equipment is generally difficult. However, in order to shorten the period of thermal design, more detailed investigation about airflow characteristics around the fans mounted in high-density packing electronic equipment should be done in order to achieve the accurate prediction of fans supply flow rate easily. We are trying to develop a prediction model of accurate supply flow rate of the fans mounted in high-density packaging electronic equipment. In this report, the pressure drop characteristic near the axial fan when an obstruction, which simulates electrical components mounted near the fans, is mounted in front of the fan was evaluated while changing the type of the obstruction. The pressure drop around the fan with the obstruction is mainly composed of three factors; the pressure drop around the obstruction, the inlet pressure drop at the fan and the outlet pressure drop from the fan. A level of these pressure drop factors were evaluated quantitatively by comparing experimental results with the conventional pressure drop database. In order to evaluate the accurate supply flow rate of the fan in high-density packaging electronic equipment, an important factor was clarified from the viewpoint of the pressure drop characteristics around the fans.

Flow Resistance Network Analysis in Fan-Cooled High-Density Packaging Electronic Equipment

This study describes an application of the flow resistance network analysis to thermal design of fan-cooled electronic equipment. Especially, a modeling method of the flow resistance network was investigated. Current electronic equipment becomes smaller and thinner while their functions become more complex. As a result, flow passages for cooling air become complex. In order to simulate the complex airflow in high-density packaging electronic equipment by using the flow resistance network, we tried to develop the flow resistance network by support of the 3D-CFD analysis. A test model which simulates high-density packaging electronic equipment is prepared and the flow resistance network analysis is applied to the prediction of flow rate distribution in the model. Through the investigation, we obtained information and future problems about the development of the flow resistance network in electronic equipment with lots of electrical components.Copyright

Thermal modeling of electronic components for thermal simulation of electronic equipment

Thermal flow simulation based on computational fluid dynamics (CFD) is applied to the thermal design of electronic equipment. This paper discusses the applicability of the multiple reference frame (MRF) approach, which is a new method for modeling an axial cooling fan, to the thermal flow simulation of electronic equipment. In this study, we performed flow visualization of the exhaust air flow pattern of the fan plane and then we compared the flow visualization results with the MRF fan model simulation results. Finally, comparing the P-Q characteristic which obtained by MRF fan model simulation with measured P-Q characteristic was conducted to validate the applicability of the MRF approach to the thermal flow simulation of electronic equipment.