https://dspace.library.uu.nl/bitstream/handle/1874/212953/strange_epjc.pdf;sequence=2

The ALICE Collaboration

The depletion of the world's limited reservoirs of fossil fuels, the worldwide impact of global warming and the high cost of energy are among the primary issues driving a renewed interest in the capture and reuse of waste energy. A major source of waste energy is being created by data centers through the increasing demand for cloud based connectivity and performance. In fact, recent figures show that data centers are responsible for more than 2% of the US total electricity usage. Almost half of this power is used for cooling the electronics, creating a significant stream of waste heat. The difficulty associated with recovering and reusing this stream of waste heat is that the heat is of low quality. In this paper, the most promising methods and technologies for recovering data center low-grade waste heat in an effective and economically reasonable way are identified and discussed. A number of currently available and developmental low-grade waste heat recovery techniques including district/plant/water heating, absorption cooling, direct power generation (piezoelectric and thermoelectric), indirect power generation (steam and organic Rankine cycle), biomass co-location, and desalination/clean water are reviewed along with their operational requirements in order to assess the suitability and effectiveness of each technology for data center applications. Based on a comparison between data centers' operational thermodynamic conditions and the operational requirements of the discussed waste heat recovery techniques, absorption cooling and organic Rankine cycle are found to be among the most promising technologies for data center waste heat reuse.

A review of data center cooling technology, operating conditions and the corresponding low-grade waste heat recovery opportunities

Continued miniaturization and demand for high-end performance of electronic devices and appliances have led to dramatic increase in their heat flux generation. Consequently, conventional coolants and cooling approaches are increasingly falling short in meeting the ever-increasing cooling needs and challenges of those high heat generating electronic devices. This study provides a critical review of traditional and emerging cooling methods as well as coolants for electronics. In addition to summarizing traditional coolants, heat transfer properties and performances of potential new coolants such as nanofluids are also reviewed and analyzed. With superior thermal properties and numerous benefits nanofluids show great promises in fulfilling the cooling demands of high heat generating electronic devices. It is believed that applications of such novel coolants in emerging techniques like micro-channels and micro-heat pipes can revolutionize cooling technologies for electronics in the future.

A critical review of traditional and emerging techniques and fluids for electronics cooling

Thermal management is one of the main challenges for the future of electronics1–5. With the ever-increasing rate of data generation and communication, as well as the constant push to reduce the size and costs of industrial converter systems, the power density of electronics has risen6. Consequently, cooling, with its enormous energy and water consumption, has an increasingly large environmental impact7,8, and new technologies are needed to extract the heat in a more sustainable way—that is, requiring less water and energy9. Embedding liquid cooling directly inside the chip is a promising approach for more efficient thermal management5,10,11. However, even in state-of-the-art approaches, the electronics and cooling are treated separately, leaving the full energy-saving potential of embedded cooling untapped. Here we show that by co-designing microfluidics and electronics within the same semiconductor substrate we can produce a monolithically integrated manifold microchannel cooling structure with efficiency beyond what is currently available. Our results show that heat fluxes exceeding 1.7 kilowatts per square centimetre can be extracted using only 0.57 watts per square centimetre of pumping power. We observed an unprecedented coefficient of performance (exceeding 10,000) for single-phase water-cooling of heat fluxes exceeding 1 kilowatt per square centimetre, corresponding to a 50-fold increase compared to straight microchannels, as well as a very high average Nusselt number of 16. The proposed cooling technology should enable further miniaturization of electronics, potentially extending Moore’s law and greatly reducing the energy consumption in cooling of electronics. Furthermore, by removing the need for large external heat sinks, this approach should enable the realization of very compact power converters integrated on a single chip. Cooling efficiency is greatly increased by directly embedding liquid cooling into electronic chips, using microfluidics-based heat sinks that are designed in conjunction with the electronics within the same semiconductor substrate.

/pdf/co-designing-electronics-with-microfluidics-for-more-5aa1udo1ts.pdf

Co-designing electronics with microfluidics for more sustainable cooling.

Towards hybrid nanofluids: Preparation, thermophysical properties, applications, and challenges

The purpose of this literature review is to compare different cooling technologies currently in development in research laboratories that are competing to solve the challenge of cooling the next generation of high heat flux computer chips. Today, most development efforts are focused on three technologies: liquid cooling in copper or silicon micro-geometry heat dissipation elements, impingement of liquid jets directly on the silicon surface of the chip, and two-phase flow boiling in copper heat dissipation elements or plates with numerous microchannels. The principal challenge is to dissipate the high heat fluxes (current objective is 300 W/cm2) while maintaining the chip temperature below the targeted temperature of 85°C, while of second importance is how to predict the heat transfer coefficients and pressure drops of the cooling process. In this study, the state of the art of these three technologies from recent experimental articles (since 2003) is analyzed and a comparison of the respective merits and ...

State of the Art of High Heat Flux Cooling Technologies

Critical heat flux in multi-microchannel copper elements with low pressure refrigerants

Experimental study on condensation heat transfer in vertical minichannels for new refrigerant R1234ze(E) versus R134a and R236fa

This article investigates the effect of inlet orifices on saturated critical heat flux (CHF) in multi-microchannel heat sinks. Two different multi-microchannel heat sinks made in copper were tested with three low pressure refrigerants (R134a, R236fa, R245fa). One had 20 parallel rectangular microchannels of 467 × 4052 μm (width × depth) while the other had 29 channels of 199 × 756 μm (width × depth). Flow visualization has been conducted with and without an orifice insert at the inlet of microchannels. Visualization confirmed the existence of flow instability, back flow and non-uniform distribution of flow among the channels when the insert with orifices was removed. Flow patterns in the microchannels and their evolution with increasing heat flux were observed. The flow boiling curves suggest that in the case of omitting the orifice, the boiling incipient occurred at a higher heat flux resulting in a higher overshoot of wall temperature. Moreover, the flow was easily subjected to instability and caused CHF to occur at much lower values than occurred with the orifices in place.

Effect of inlet orifice on saturated CHF and flow visualization in multi-microchannel heat sinks

Note: Keynote speaker Reference LTCM-CONF-2007-007View record in Web of Science Record created on 2007-11-10, modified on 2017-05-10

Jung Eung Park

Papers

State of the Art of High Heat Flux Cooling Technologies

Critical heat flux in multi-microchannel copper elements with low pressure refrigerants

Experimental study on condensation heat transfer in vertical minichannels for new refrigerant R1234ze(E) versus R134a and R236fa

Effect of inlet orifice on saturated CHF and flow visualization in multi-microchannel heat sinks

Recent Advances in Thermal Modeling of Micro-Evaporators for Cooling of Microprocessors