Thermostat

Un thermostat est un dispositif permettant de maintenir un système (appareil, machine, moteur) à une température relativement stable. Historique Warren S. Johnson dépose un brevet concernant le thermostat en 1883. Le thermostat a été développé en 1886 par Albert Butz, qui a donné naissance à la société Honeywell. Il permettait de commander une trappe d'arrivée d'air sur une chaudière à charbon pour « réguler » sa température. Dans le contexte du dérèglement climatique, des bulles de chaleur urbaines mais aussi des besoins de sobriété énergétique liées aux crises successives de l'énergie, les thermostats sont devenus courants voire obligatoires sur les radiateurs et autres systèmes de chauffage ou de climatisation (ex. : un décret de juin 2023 impose en France que tous les systèmes de refroidissement des bâtiments tertiaires et résidentiels, neufs ou existants, soient tous équipés de systèmes de régulation de la température au premier janvier 2027. Le décret impose aus

A finite-temperature dynamic coupled atomistic/discrete dislocation method

William Curtin, Ronald Earle Miller

A method for simultaneously thermostatting an atomistic region and absorbing energetic pulses impinging on the atormstic/continuum interface from the atomistic region is developed to operate within the framework of the coupled atomistic/discrete dislocation method. The approach inserts an additional Langevin damping term and a random force term into the equations of motion for atoms in a 'stadium' boundary region near the atom/continuum interface, with the damping coefficient ramped linearly over the width of the region, as suggested by Holian and Ravelo. The remaining interior atom dynamics are computed using a standard MD algorithm with no artificial damping or thermostatting. The continuum region deformations are computed using static FEM updated stochastically over time scales comparable to the Debye frequency of the atoms using time-averaged displacements at the atom/continuum interface, thereby providing an evolution of the continuum region that tracks the atomistic deformation. The method is evaluated by studying the ability of the coupled system: (i) to equilibrate the inner atomistic region at a desired temperature under conditions of no external or internal loading, (ii) to produce the proper canonical thermal fluctuations and (iii) to absorb deformation pulses initiated in the interior region and incident upon the atomistic/continuum boundary. With an optimal maximum damping coefficient of approximately 1/2 of the Debye frequency, temperature stability is attained at values very close to the target temperature. The temperature variance agrees well with the canonical expectation for various temperatures. For the same damping parameters and at low temperature, high-energy deformation pulses propagate unimpeded up to the stadium boundary region and then are completely damped out upon approach to the atomistic/continuum interface with no measurable reflections. At higher temperatures, thermal fluctuations in the total energy make analyses difficult, but damping of high-energy deformation pulses is achieved within the limits of the thermal noise in the system while observation of the time-dependent displacements shows no observable reflections.

2005

Design Of Passive Two-Phase Thermosyphons For Server Cooling

Raffaele Luca Amalfi, Filippo Cataldo, Jackson Braz Marcinichen, John Richard Thome

The main objective of this paper is to utilize an improved version of the simulator presented at InterPACK 2017 to design a thermosyphon system for energy-efficient heat removal from 2-U servers used in high-power datacenters. Currently, between 25% and 45% of the total energy consumption of a datacenter (this number does not include the energy required to drive the fans at the server-level) is dedicated to cooling, and with a predicted annual growth rate of about 15% (or higher) coupled with the plan of building numerous new datacenters to handle the "big data" storage and processing demands of emerging 5G networks, artificial intelligence, electrical vehicles, etc., the development of novel, high efficiency cooling technologies becomes extremely important for curbing the use of energy in datacenters. Notably, going from air cooling to two-phase cooling, not only enables the possibility to handle the ever higher heat fluxes and heat loads of new servers, but it also provides an energyefficient solution to be implemented for all servers of a datacenter to reduce the total energy consumption of the entire cooling system. In that light, a pseudo -chip with a footprint area of 4 x 4 cm2 and a maximum power dissipation of 300 W (corresponding heat flux of about 19 W/cm2), will be assumed as a target design for our novel thermosyphon-based cooling system. The simulator will be first validated against an independent database and then used to find the optimal design of the chip's thermosyphon. The results demonstrate the capability of this simulator to model all of the thermosyphon's components (evaporator, condenser, riser and downcomer) together with overall thermal performance and creation of operational maps. Additionally, the simulator is used here to design two types of passive two-phase systems, an air- and a liquid-cooled thermosyphon, which will be compared in terms of thermal -hydraulic performance. Finally, the simulator will be used to perform a sensitivity analysis on the secondary coolant side conditions (inlet temperature and mass flow rate) to evaluate their effect on the system performance.

AMER SOC MECHANICAL ENGINEERS2020

Design Of Passive Two-Phase Thermosyphons For Server Cooling

Raffaele Luca Amalfi, Filippo Cataldo, Jackson Braz Marcinichen, John Richard Thome

AMER SOC MECHANICAL ENGINEERS2020

A finite-temperature dynamic coupled atomistic/discrete dislocation method

William Curtin, Ronald Earle Miller

2005

Optimal Hysteresis for Deteriorating Two-armed Bandit Problem with Switching Costs

A finite-temperature dynamic coupled atomistic/discrete dislocation method

Design Of Passive Two-Phase Thermosyphons For Server Cooling

Design Of Passive Two-Phase Thermosyphons For Server Cooling

Optimal Hysteresis for Deteriorating Two-armed Bandit Problem with Switching Costs

A finite-temperature dynamic coupled atomistic/discrete dislocation method