110th Anniversary: Design of Cooling Fluids for Electronic Equipment

Abstract

Miniaturization technologies have led to a dramatic increase in electronics cooling requirements, which traditional cooling approaches are unable to fulfill. Thus, it is necessary to identify working fluids that enhance cooling performance and meet environmental and safety requirements. In this work, we develop a computer-aided molecular design approach to identify working fluids that have better heat transfer performance than the industrial refrigerant HFE 7200. We use group contribution methods as the major property estimation tool along with additional accurate property models. We derive a metric to measure the cooling performance of a two-phase cooling system consisting of microchannel heat sinks. Utilizing metrics for biodegradability and lethal concentration (LC50) enables additional analysis of the candidate molecules. Finally, we provide predictions of chemical stability to minimize the risk of potential chemical transformation. As a result of this work, we identify a number of novel cooling fluids that fall into four organic families.

A New Functional Group Selection Method for Group Contribution Models and Its Application in the Design of Electronics Cooling Fluids

“…We seek replacement coolants with better heat transfer properties than the commercial coolant Novec HFE7200 and develop a set of property targets listed in Table . This set of design targets was identified in our previous work . In a two-phase cooling system, coolant vaporizes to absorb sufficient heat from the electronics to maintain a chip temperature below 85 °C .…”

“…The following metric, developed in Sun et al., is used here to evaluate the performance of microchannel two-phase cooling fluids: The metric is formulated as the ratio of heat transfer coefficient (HT) and pressure drop (PD) to maximize heat transfer rate while minimizing pressure drop across microchannels to guarantee phase change occurs throughout the cooling system.…”

“…The CAMD approach builds on methodologies that solve two problems: the “forward problem” relies on semiempirical quantitative structure–property relationships (QSPRs) to predict properties given molecular structures, while the “backward problem” chooses optimal molecules from the space of theoretically possible chemical structures given target properties. These two problems represent different sides of the CAMD puzzle and have attracted significant attention, especially in the context of specific applications, including the design of alternative refrigerants, − heat transfer fluids, − extraction solvents, − polymer repeating units, − mixtures, − reaction solvents, − ionic liquids, ,− and pharmaceutical solvents. , …”

“…Existing commercial coolants such as Novec fluid HFE7100 and HFE7200 are limited in their ability to remove high heat flux from compact spaces. , Therefore, interest emerges in developing new cooling fluids with high heat removal capability. This problem is a perfect application area for CAMD and has been studied extensively in the past three decades. ,,,,− Organosilicon compounds generally demonstrate high heat conductivity, high electrical insulation, and low viscosity. These traits have motivated us to consider organosilicon compounds as part of the set of candidate replacements for existing coolants.…”

“…In our past approaches to coolant design, we relied extensively on GC+ to identify potential molecular designs. We studied microchannel cooling regimes and identified a number of promising coolants that are environmentally friendly, safe to operate, and more heat transfer efficient than HFE7200 . Unfortunately, GC+ was built with only 42 measurements involving organosilicon compounds; most Si groups were involved in no more than two measurements for most properties of interest, which makes use of this GC+ model unreliable for silicon-based structures.…”