Shell heat loss

The SPWR adopts a water-filled CV. The RPV is covered with a water-tight shell. A mirror insulator of laminated thin stainless steel plates is mounted inside the shell. Heat loss is estimated to be below 1 MW. The space between the water-tight shell and the RPV corresponds to a drywell of the suppression type CV of conventional BWRs. To allow for a pipe rupture in this space, the shell is equipped with pressure relief valves. The advantages of the water-filled CV are the compactness of the reactor plant and ease of application of a passive decay heat removal system. 

AH the reduction reactions are endothermic, regardless of the reductant used. The heat for these reactions, along with the requirements for the sensible heats of the hot metal and slag, and heat losses through the furnace shell, is provided by the heat generated from equation 1 plus the sensible heat of the hot blast. 

Rotating equipment, except brick-hned vessels, operated above ambient temperatures is usually insulated to reduce heat losses. Exceptions are direct-heat units of bare metal construction operating at high temperatures, on which heat losses from the shell are neces-saiy to prevent overheating of the metal. Insulation is particularly necessary on cocurrent direct-heat units. It is not unusual for product cooling or condensation on the shell to occur in the last 10 to 50 percent of the cylinder length if it is not well insulated. 

Equal surfaces in each shell pass or tube pass. Negligible heat loss to surroundings or internally between passes. 

While vitally necessary, blowdown can be expensive in terms of lost heat. Therefore a point will be reached when it is economical to install a blowdown heat recovery system. Generally, the heat content in the blowdown water for a shell boiler will represent only about 25 per cent of the heat content in the same percentage of steam. Therefore, if a blowdown rate of 10 per cent is required this represents an approximate heat loss of 2.5 per cent from the boiler capacity. This differential reduces and eventually becomes insignificant on high-pressure watertube boilers. 

At the heart of an automotive catalytic converter is a catalyzed monolith which consists of a large number of parallel channels in the flow direction whose walls are coated with a thin layer of catalyzed washcoat. The monolith catalyst brick is wrapped with mat, steel shell and insulation to minimize exhaust gas bypassing and heat loss to the surroundings. 

Fluid temperatures. If the temperatures are high enough to require the use of special alloys placing the higher temperature fluid in the tubes will reduce the overall cost. At moderate temperatures, placing the hotter fluid in the tubes will reduce the shell surface temperatures, and hence the need for lagging to reduce heat loss, or for safety reasons. 

A differential pressure sensor monitors the pressure drop across the reactor, giving also an indication of the coke formation. The outside shell of the reactor is thermally insulated to limit heat loss. 

Spherical Shell. Radial heat flux, qr, at any radius r through a spherical shell of inner radius r, held at temperature Th and outer radius r0 held at temperature Ta, e.g. heat loss through the wall of a storage sphere, is given by... 

A) The outside of the shell is insulated, and there is no heat loss from the shell. 

Consider a spherical container of inner radius = 8 cm, outer radius fa = 10 ern, and thermal conductivity A = 45 W/m C, as shown in Fig. 2-52. The inner and outer surfaces of the container are maintained at constant temperatures of Ti = 200 0 and T2 - 80°C, respectively, as a result of some chemical reactions occurring inside. Obtain a general relation for the temperature distribution inside the shell under steady conditions, and determine the rate of heat loss from the container. 

Steam a T i = 320°C flows in a cast iron pipe (k = 80 W/m °C) whose inner and outer diameters are D, = 5 cm and Dj 5.5 cm, respectively. The pipe is covered with 3-cm-thick glass wool insulation with k = 0.05 W/m C. Heat is lost to the surroundings at - 5°C by natural convection and radiation, with a cyimblned heat transfer coefficient of hj = 18 W/m °C. Taking the heat transfer coefficient inside the pipe to be hi = 60 W/m °C, determine the rate of heat loss from the steam per unit length of the pipe. Also determine the temperature drops across the pipe shell and the insulation. 

---