Process description for the U4 example simulation

The cooling tower provides cooling water at 20.5°C (69°F) based on a wet-bulb temperature (WBT) of 23.3°C (74°F) and a cooling tower approach of 2.8°C (5°F).

The design requirements are:

• The minimum pipe velocity is1m/s (3 ft/s) to avoid deposition of sediments

• The maximum pipe velocity is 3.7 m/s (12 ft/s) to avoid erosion

• The maximum outlet temperature of the heat exchanger cooling water is 45°C (113°F).

• The cooling water pump has not been selected. That is, both pumps are operating.

• The pipe roughness is 0.0046 mm (0.0018 in).

  The following table provides a summary of the existing heat exchanger design, which includes the required heat duty and the pressure drop information. We obtain the reference pressure drop and reference flow from the heat exchanger data sheets so that we can calculate the actual pressure drops by relating the pressure drop changes to the square of the flow rate.

  Heat Exchanger	Required Duty		Reference Flow		Pressure Drop at Reference Flow
  	(kW)	(MMBtu/hr)	(kg/hr)	(lb/hr)	(kPa)	(psi)
  E11	927.5	3.165	80430	177318	68.6	9.95
  E12	538.5	1.837	46715	102989	68.6	9.95
  E14	744.2	2.539	64562	142335	68.6	9.95
  E15	462.6	1.578	40135	88482	68.6	9.95
  E20	1779.9	6.073	63170	139266	68.6	9.95
  E20A	1116.7	3.810	39636	87382	68.6	9.95
  E22	1780.7	6.076	63198	139328	68.6	9.95
  E22A	1117	3.811	39645	87402	68.6	9.95
  E27	3567.6	12.173	126618	279145	68.6	9.95
  E28	1930.7	6.588	68525	151072	68.6	9.95
  E30	2944.4	10.047	104503	230389	68.6	9.95
  E31	1626.1	5.548	57715	127240	68.6	9.95
  E4	649.2	2.215	39182	86381	68.6	9.95
  E4A	649.2	2.215	39179	86375	68.6	9.95
  E6	910.3	3.106	54933	121106	68.6	9.95
  E7A	1633.1	5.572	98548	217261	68.6	9.95

Heat exchangers E11, E12, E14, and E15 are in series to E7A, E6, E4, and E4A. Heat exchangers E7A, E6, E4, and E4A do not need as cold of cooling water. This series configuration reduces the required cooling water compared to a completely parallel network.