Co-current-flow heat exchanger

Two different types of heat exchangers can be identified. In the co-current-flow heat exchanger, both fluids flow in the same direction, as shown in Figure 9. In this case, the two fluids enter the heat exchanger from the same end. 

Figure 9 Schematic representation of a co-current-flow heat exchanger...

Comparison between Co-Current-Flow and Counter-Current-Flow Heat Exchangers. The worked examples reported below will demonstrate the different efficiencies of the two heat exchanger configurations in terms of the heat transfer area required in both cases for the same U. Let us consider two fluids between which heat is being... 

A heat exchanger is required to cool 20 kg/s of water from 360 K to 340 K by means of 25 kg/s water entering at 300 K. If the overall coefficient of heat transfer is constant at 2 kW/m2K, calculate the surface area required in < a) a countercurrent concentric tube exchanger, and (b) a co-current flow concentric tube exchanger. 

Considering co-current flow as shown in Figure 9.84c/, for an elemental area AA of a heat exchanger, the rate of transfer of heat AQ is given by ... 

After plant modifications, the heat exchanger is incorrectly connected so that the two streams are in co-current flow. What are the new outlet temperatures of hydrocarbon and water, if the overall heat transfer coefficient is unchanged ... 

For the co-current-flow configuration, the temperature difference AT is large at the inlet but decreases exponentially towards the outlet. The temperature of the hot fluid decreases and the temperature of the cold fluid increases along the heat exchanger. The outlet temperature of the cold fluid can never exceed that of the hot fluid, no matter how long the heat exchanger is. 

The flow arrangement in shell-and-tube heat exchangers can involve both co-current-flow and counter-current-flow, as shown in the schematic in Figure 17. 

As a consequence of the channel head tube-side inlet and outlet being located on the same end of the exchanger, the lower half of the shell is in co-current flow. Depending on the temperature profile, this typically reduces the LMTD by 5 to 25 percent. To calculate this loss in heat-transfer efficiency due to this problem, we use the F-factor correction factor as presented in your TEMA Data Book. 

In Example 11-3, we solved for the temperature as a function of conversion and then used that relationship to calculate k and An easier way is to solve the general or base case of a heat exchanger for co-current flow and write the corresponding Polymath program. Next use Polymath [Part (a), but multiply the parameter Uei by zero, i.e.. 

The basic flow patterns in a heat exchanger are countercurrent How, co-cunent (parallel) flow, and cross flow, see Figure 2, For oountercuiient flow pattern, two flow streams are flowing in opposite direction to each other. For co-current flow pattern, two flow streams are flowing in the same direction. For cross flow pattern, two flow streams are flowing at an angle to each other. 

For heat exchangers in true counter-current (fluids flowing in opposite directions inside or outside a tube) or true co-current (fluids flowing inside and outside of a tube, parallel to each other in direction), with essentially constant heat capacities of the respective fluids and constant heat transfer coefficients, the log mean temperature difference may be appropriately applied, see Figure 10-33. ... 

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