Effective heat exchange area

A more practical way to estimate the effective heat exchange area consists in considering the sum of the channel width and the wall thickness as shown in Equation 5.17. 

The heatable areas of the diyer are the vessel wall and the screw. The diyer makes maximum use of the product-heated areas—the filling volume of the vessel (up to the knuckle of the dished head) is the usable product loading. The top cover of the vessel is easily heated by either a half-pipe coil or heat tracing, which ensures that no vapor condensation will occur in the process area. In addition to the conical vessel heated area, heating the screw effectively increases the heat exchange area by 15-30 percent. This is accomphshed via rotary joints at the base of the screw. The screw can be neated with the same... 

Plates are available with effective heat transfer area from 0.03 to 3.5 m and up to 700 can be contained within the frame of the largest plate-type heat exchanger, providing over 2400 m of surface area. Flow ports and associated pipework are sized in proportion to the plate area and control the maximum liquid throughput. 

The four packed beds are in effect heat exchangers of very high surface area but of minimal cost and are very compact. 

With single irreversible second-order reactions, the maximum of the heat release rate is reached at the beginning of the feed. At this stage, the heat exchange area may only be partially used, due to the increasing volume. This limits the effective available cooling capacity. Therefore, the knowledge of the maximum heat release... 

In principle, however, the effective surface area for heat transfer from the single monomer is decreased by the contact area between the particles. The fractal dimension of the aggregates varies in different systems and depends on the evolution process. For dense aggregates, heat transfer rates are decreased due to the reduced heat exchange area compared to primary particles only connected by point contact in a chain like structure (Liu et al., 2006a-c). This leads to an overestimation of... 

The authors pose the problem as a multiple objective function problem, and, in their example, consider the two competing objectives of total evaporator heat exchanger area and steam usage. The paper is really a clever way of eliminating a number of flow patterns as never being candidates for the optimal solution regardless of the relative importance of the cost for area versus steam costs. For a particular triple effect example problem, they show that, depending on the liquid feed temperature, 3,... 

A shell-and-tube heat exchanger is used as an ammonia condenser with ammonia vapor entering the shell at 50°C as a saturated vapor. Water enters the single-pass tube arrangement at 20°C and the total heat transfer required is 200 kW. The overall heat-transfer coefficient is estimated from Table I0-I as 1000 W/m2 °C. Determine the area to achieve a heat exchanger effectiveness of 60 percent with an exit water temperature of 40°C. What percent reduction in heal transfer would result if the water flow is reduced in half while keeping the heat exchanger area and V the same ... 

NicoL W, Hemier, M., Hildebrant, D., Glasser, D., 2001. The attainable region and process synthesis Reaction systems with external cooling and heating. The effect of relative cost of reactor volume to heat exchange area on the optimal process layout. Chem. Eng. Sci. 56, 173-191. 

---