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1. Effect of immersion cooling parameters on thermal and electrochemical response of a Li-ion cell

   https://doi.org/10.1016/j.jpowsour.2025.236285  

   Tripathi, Piyush Mani; Marconnet, Amy M (March 2025, Journal of Power Sources)

   Forced immersion cooling, where a dielectric fluid flows in contact with the cells, is an effective cooling approach for lithium-ion batteries. While previous models demonstrated effectiveness, they generally focused on thermal-fluid aspects and often neglected the coupling between temperature, cell potential, and heat generation (in other words, the electrochemistry remained unaffected by cooling conditions). Here, we use a fully coupled modeling approach that solves the detailed electrochemical model (with temperature-dependent properties) in conjunction with the thermal-fluid transport models at each time step. For an 18650 cell, we compare forced immersion cooling (water and mineral oil) to forced air cooling. Improved temperature control with immersion cooling leads to higher heat generation with increased capacity loss: a 3 K temperature rise corresponds to 10% loss, whereas 42 K temperature rise results in 0.4% loss at 5C discharge. Neglecting two-way coupling prohibits accurate analysis of the effectiveness of immersion cooling. Furthermore, the thermal conductivity and heat capacity of the fluid most significantly impact the electrochemical and thermal response. Finally, we define a new metric to compare performance with different flow parameters without computationally-expensive numerical simulations. Overall, this study provides insights that will be useful in understanding and design of immersion-cooled battery systems. 

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2. Measurement of the Thermal Performance of a Custom-Build Single-Phase Immersion Cooled Server at Various High and Low Temperatures for Prolonged Time

   https://doi.org/10.1115/1.4045156  

   Bansode, Pratik V.; Shah, Jimil M.; Gupta, Gautam; Agonafer, Dereje; Patel, Harsh; Roe, David; Tufty, Rick (March 2020, Journal of Electronic Packaging)

   Abstract The next radical change in the thermal management of data centers is to shift from conventional cooling methods like air-cooling to direct liquid cooling to enable high thermal mass and corresponding superior cooling. There has been in the past few years a limited adoption of direct liquid cooling in data centers because of its simplicity and high heat dissipation capacity. Single-phase engineered fluid immersion cooling has several other benefits like better server performance, even temperature profile, and higher rack densities and the ability to cool all components in a server without the need for electrical isolation. The reliability aspect of such cooling technology has not been well addressed in the open literature. This paper presents the performance of a fully single-phase dielectric fluid immersed server over wide temperature ranges in an environmental chamber. The server was placed in an environmental chamber and applied extreme temperatures ranging from −20 °C to 10 °C at 100% relative humidity and from 20 to 55 °C at constant 50% relative humidity for extended durations. This work is a first attempt of measuring the performance of a server and other components like pump including flow rate drop, starting trouble, and other potential issues under extreme climatic conditions for a completely liquid-submerged system. Pumping power consumption is directly proportional to the operating cost of a data center. The experiment was carried out until the core temperature reached the maximum junction temperature. This experiment helps to determine the threshold capacity and the robustness of the server for its applications in extreme climatic conditions. 

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3. A Numerical Study Comparing Forced and Natural Convection in a High-Density Single-Phase Immersed Cooled Server

   https://doi.org/10.1115/IPACK2023-112065  

   Gupta, Gautam; Nair, Vivek; Bansode, Pratik; Suthar, Rohit; Pundla, Sai Abhideep; Herring, Joseph; Lamotte-Dawaghreh, Jacob; Sivaraju, Krishna Bhavana; Agonafer, Dereje; Mynampati, Poornima; et al (October 2023, American Society of Mechanical Engineers)

   Abstract Data centers are witnessing an unprecedented increase in processing and data storage, resulting in an exponential increase in the servers’ power density and heat generation. Data center operators are looking for green energy efficient cooling technologies with low power consumption and high thermal performance. Typical air-cooled data centers must maintain safe operating temperatures to accommodate cooling for high power consuming server components such as CPUs and GPUs. Thus, making air-cooling inefficient with regards to heat transfer and energy consumption for applications such as high-performance computing, AI, cryptocurrency, and cloud computing, thereby forcing the data centers to switch to liquid cooling. Additionally, air-cooling has a higher OPEX to account for higher server fan power. Liquid Immersion Cooling (LIC) is an affordable and sustainable cooling technology that addresses many of the challenges that come with air cooling technology. LIC is becoming a viable and reliable cooling technology for many high-power demanding applications, leading to reduced maintenance costs, lower water utilization, and lower power consumption. In terms of environmental effect, single-phase immersion cooling outperforms two-phase immersion cooling. There are two types of single-phase immersion cooling methods namely, forced and natural convection. Here, forced convection has a higher overall heat transfer coefficient which makes it advantageous for cooling high-powered electronic devices. Obviously, with natural convection, it is possible to simplify cooling components including elimination of pump. There is, however, some advantages to forced convection and especially low velocity flow where the pumping power is relatively negligible. This study provides a comparison between a baseline forced convection single phase immersion cooled server run for three different inlet temperatures and four different natural convection configurations that utilize different server powers and cold plates. Since the buoyancy effect of the hot fluid is leveraged to generate a natural flow in natural convection, cold plates are designed to remove heat from the server. For performance comparison, a natural convection model with cold plates is designed where water is the flowing fluid in the cold plate. A high-density server is modeled on the Ansys Icepak, with a total server heat load of 3.76 kW. The server is made up of two CPUs and eight GPUs with each chip having its own thermal design power (TDPs). For both heat transfer conditions, the fluid used in the investigation is EC-110, and it is operated at input temperatures of 30°C, 40°C, and 50°C. The coolant flow rate in forced convection is 5 GPM, whereas the flow rate in natural convection cold plates is varied. CFD simulations are used to reduce chip case temperatures through the utilization of both forced and natural convection. Pressure drop and pumping power of operation are also evaluated on the server for the given intake temperature range, and the best-operating parameters are established. The numerical study shows that forced convection systems can maintain much lower component temperatures in comparison to natural convection systems even when the natural convection systems are modeled with enhanced cooling characteristics. 

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4. Parameters of performance: A deep dive into liquid-to-air CDU assessment

   https://doi.org/10.1016/j.csite.2024.105461  

   Heydari, Ali; Gharaibeh, Ahmad R; Tradat, Mohammad; Soud, Qusai; Manaserh, Yaman; Radmard, Vahideh; Eslami, Bahareh; Rodriguez, Jeremy; Sammakia, Bahgat (December 2024, Case Studies in Thermal Engineering)

   The rapid growth in data center workloads and the increasing complexity of modern applications have led to significant contradictions between computational performance and thermal management. Traditional air-cooling systems, while widely adopted, are reaching their limits in handling the rising thermal footprints and higher rack power densities of next-generation servers, often resulting in thermal throttling and decreased efficiency, emphasizing the need for more efficient cooling solutions. Direct-to-chip liquid cooling with cold plates has emerged as a promising solution, providing efficient heat dissipation for high-performance servers. However, challenges remain, such as ensuring system stability under varying thermal loads and optimizing integration with existing infrastructure. This comprehensive study digs into the area of data center liquid cooling, providing a novel, comprehensive experimental investigation of the critical steps and tests necessary for commissioning coolant distribution units (CDUs) in direct-to-chip liquid-cooled data centers. It carefully investigates the hydraulic, thermal, and energy aspects, establishing the groundwork for Liquid-to-Air (L2A) CDU data centers. A CDU’s performance was evaluated under different conditions. First, the CDU’s maximum cooling capacity was evaluated and found to be as high as 89.9 kW at an approach temperature difference (ATD) of 18.3 ◦C with a 0.83 heat exchanger effectiveness. Then, to assess the cooling performance and stability of the CDU, a low-power test and a transient thermohydraulic test were conducted. The results showed instability in the supply fluid temperature (SFT) caused by the oscillation in fan speed at low thermal loads. Despite this, heat removal rates remained constant across varying supply air temperatures (SATs), and a partial power usage effectiveness (PPUE) of 1.042 was achieved at 100 % heat load (86 kW) under different SATs. This research sets a foundation for improving L2A CDU performance and offers practical insights for overcoming current cooling limitations in data centers. 

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5. A computationally efficient approach for immersion cooling of a Li-Ion battery cell

   https://doi.org/10.1016/j.icheatmasstransfer.2025.108856  

   Tripathi, Piyush Mani; Marconnet, Amy (May 2025, International Communications in Heat and Mass Transfer)

   Immersion-cooled battery thermal management systems (BTMSs) are generally designed and analyzed using numerical simulations. These models must couple the electrochemical and thermal–fluid physics for accurate results. However, such a numerical approach is computationally expensive and may not be feasible, particularly for large systems. Here, we develop a computationally efficient approach to study immersion cooling-based BTMSs with the coupled physics. After validating the simplified immersion-cooled battery model for fixed convection coefficient, we then define two simplified immersion cooling models: one using existing heat transfer correlations and the other employing customized correlations trained from fully-coupled numerical models. The trained models are highly accurate (error <3%). Moreover, they are very flexible as they can be formulated to study different combinations of mass flow rates, fluids, and discharge rates using a single heat transfer correlation. Additionally, the trained models are data-frugal, requiring only data from two mass flow rates (for a given fluid and discharge rate) to predict the response for other mass flow rates. The significant reduction in computation cost [from hours or days for the fully-coupled numerical models to seconds for proposed models] makes the proposed approach more suitable for rapid analysis, optimization, and real-time implementation of the immersion-cooled BTMSs. 

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