Natural convection cooling

Bar-Cohen, A. and Rohsenow, W.M.. "Thermally Optimum Spacing of Vertical Natural Convection Cooled, Parallel Plates , J. Heat Transfer, Vol. 106. p. 116. 1984. 

The thermal simulation was verified by choosing a benzene concentration of zero (no reaction) and natural convection cooling only. An ambient temperature of 20°C was assumed and, to minimise calcur-lation time, the accumulation terms in the separation regions were neglected. For a 1.2 kW power input, the model predicted a steady-state catalyst temperature of 473°C which was reached about seven hours after heating was begun. A temperature loss of 42 0 between the pebble benzene mixer and the catalyst was predicted while the difference between the catalyst and the fluidized bed preheater was 57 C. This loss was attributed to the increased... 

Natural Convection Cooling cf Finned Surfaces (/inconstant) 517... 

As we have discussed earlier, the buoyancy force is caused by the density difference between the healed (or cooled) fluid adjacent to the surface and tiie fluid surrounding it, and is proportional to this density difference and the volume occupied by the warmer fluid. It is also well knowu ll at whenever Iwc bodies in contact (.solid--solid, solid-fluid, or fluid-fluid) move relative to cacf other, a friction force develops at the contact surface in the direction opposite ic that of the motion. This opposing force slows down the fluid and thus reduce the flow rate of the fluid. Under steady conditions, the airflow rate driven b buoyancy is established at the point where these two effects balance each othet The friction force increases as more and more solid surfaces are introduced, se tiously disrupting the fluid flow and heat transfer. For that reason, heat sink with closely spaced fins are not suitable for natural convection cooling. 

Natural Convection Cooling of Vertical PCBs (f/i = constant)... 

Optimuiii Spacing of Vertical Natural Convection Cooled Parallel Plates. Journal of Heat Transfer 106 (1984),... 

B. Gebhart, Natural Convection Cooling Transients, Int. J. Heat Mass Transfer (7) 479-483,1964. 

J. H. Seely, Effect of Ultrasonics on Several Natural Convection Cooling Systems, master s thesis, Syracuse University, Syracuse, NY, 1960. 

Space limitations or high ambient temperatures may impede the use of natural convection cooling. The heat sink performance can be improved and the size reduced by a factor 2-3 using forced convection. 

To protect the foundation and to prevent softening of the hearth, open spaces are frequently provided under the hearth for air circulation—a ventilated hearth. Natural convection cooling of these spaces under a furnace is really not very effective— unless some forced flow cooling air is provided. Actually, a solid contact between furnace bottom and the earth may be better than still air cooling. If, however, the hearth is so hot that conducted heat might damage the furnace foundation, forced underside ventilation is necessary. 

Lennox, D. H., Danger of Fuel Assembly Cladding Failure with Natural Convection Cooling, ANL-EKF-18, January 5, 1950. 

Natural Convection Cooling of an Orange. An orange 102 mm in diameter... 

The thermal-hydraulic design of the rack provides sufficient natural convection cooling flow to remove 19,929 W/bundle (68,000 Btu/hrAjundle) of decay heat. 

Natural convection cooling Limits consequences Passive safety systems Reduce core damage probability... 

The thermal power of critical and subcritical facilities is so low that even immediately after the fuel is permanently discharged from the core, the cooling requirements to maintain integrity can be easily provided by natural convection cooling in air. Therefore, at any time the irradiated or spent fuel from critical facilities and very low power reactors can be properly stored in AR dry storage compartments, with no need for a decay pool. 

Note that in the literature, the total thermal resistance 0, usually under natural convection cooling conditions, is also referred to as 9j-a (junction-ambient), 6>int as 9j-c Ounction-case), and 9 xt as 9c-a (case-ambient). 

EC - elevations of the core, IHX dump HX to ensure natural convection cooling... 

Two types of air cooling — natural and forced convection — were presented in Subsection 3.2.3. fri low-heat-flux applications, natural convection cooling is the choice of physical designers. It is low in cost, easy to implement, and reliable. When the heat load is high, forced convection is the most effective cooling method. To produce the air motion, either a fan or blower is used. 

A main drain tank located below the reactor room has a natural convection cooling system. Also for decay heat removal, a reliable system such as the heat pipe could be located in the drain tank. 

ASME Code Case N-557, "In place dry annealing of a PWR nuclear reactor vessel," March, 1996. USNRC Generic Letter 92-02, Revolution of Generic Issue 79 Unanalyzed reactor vessel (PWR) thermal stress during natural convection cooling. ... 

Webster, R., Natural Convection Cooling of Liquid Metal Systems - A Review, DNR 16, AEA, Dounreay, United Kingdom, February, 1990. 

All safety related hydraulic characteristics of individual core components and of the core as a whole (such as average and local coolant velocities, and coolant pressures, as appropriate) for operational states during forced and natural convection cooling. 

Calculated Atmospheric Natural Convection Cooling of 1/2 X 4-1/2 X 48 in. Channel... 

In addition to the brief water injection, operators also tried to establish natural convection cooling as a means to cool the reactor. They had already determined that forced circulation using the reactor coolant pumps could not be established due to the large vibrations that would be caused by pumping the steam/water mixture now found throughout the reactor vessel. It was clear that operating the pumps would quickly lead to pump failure. 

For the routine experiments of two TRIGA reactors and the commissioning experiments of the new 30 MW HANARO research reactor in the Republic of Korea, a stand alone system, with input signals independent from the reactor operation and safety chaimels, is configured. This system has been utilized for the criticality approach, real time reactivity measurement, noise analyses, control rod drop time measurement, and thermal power calibration in a natural convection cooled reactor. It replaces conventional counter modules for the criticality measurement, multichannel analyzer and... 

For the case of natural convection cooled TRIGA reactors, the reactor thermal power is calibrated by measuring pool water temperature rise. A PC can measure the temperature and power monitor values during the experiment, fit temperature rise, calculate thermal power, and give calibration value for each power monitor. 

Schwartz, II., Natural Convection Cooling of Liquid Homogeneous Reactors, North. mprican. Aviation. Inc., US.AEC Report. ECU-706, Dec. 20, 1949. 

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