过程装备与控制工程外文翻译---换热器的优化选型(编辑修改稿)

过程装备与控制工程外文翻译---换热器的优化选型(编辑修改稿)内容摘要：

export under the conditions of temperature, the average temperature difference between the largest countercurrent. When the plate heat exchanger import and export of the fluid temperature difference between the two △ t1 and the difference between △ t2 not available when arithmetic average temperature (△ t1 + △ t2) / 2, General △ t1 / △ t2 less than , May be, if △ t / △ t2 for 3:00, the error is about 10 percent. the number of transfer units In the heat transfer unit of the introduction of a few dimensionless parameters NTU, known as the number of transfer units, it said plate heat exchanger of the total thermal conductivity (heat exchanger heat resistance of the countdown) and the ratio of fluid heat capacity NTU = KA / MC, it said in relation to heat fluid flow, heat transfer capacity of the heat exchanger of the size of the heat exchanger that is, nondimensional heat transfer capability. The plate heat exchanger for, KA / MC = △ t / △ tm, where △ t / △ tm known as the temperature difference than, on the right side of the process used NTUp that left the conditions of heat transfer equipment used NTUE said. NTUp is fluid temperature changes in temperature and the average ratio that is used 1 ℃ △ tm of several changes in the value of fluid temperature changes, when △ tm large, NTUp is small when △ tm hours, it has bee bigger The tendency. On the contrary, in NTUp larger in the process, △ tm of the larger temperature changes, NTUp smaller, its △ tm small changes in temperature (see table 1). Table 1 △ tm, NTUp relations △ tm large △ tm small NTUp small NTUp large NTUp large NTUp small △ tm large changes in temperature △ tm small changes in temperature Plate heat exchanger, the optimal design, is known NTUE temperature difference than the conditions, to determine a reasonable model, processes and heat transfer area, equivalent to NTUp NTUE. heat transfer process and the NTU Heating and airconditioning related to the heat transfer process if the show are as follows: ⑴ steam heating water ⑵ water water heat exchanger a. steam 133 → 133 ℃ c. a water 65 → 60 ℃ Water 5 → 65 ℃ (hot water) Secondary water 45 ← 40 ℃ (heating) b. Steam 133 → 133 ℃ d. a water 14 → 9 ℃ Water 55 → 65 ℃ (heating) secondary water 13 ← 7 ℃ (refrigeration) e. a water 29 → 24 ℃ Secondary water 26 ← 21 ℃ (refrigerator cooling) More than five cases of the process NTUp (see table 2) Table 2 heating airconditioning process of NTUp process △ tm NTUp a 133→133 ℃ 5→65 ℃ （ 65－ 5）／ ＝ b 133→133 ℃ 55→65 ℃ （ 65－ 55）／ ＝ c 65→60 ℃ 45←40 ℃ （ 45－ 40）／ 20＝ d 14→9 ℃ 13←7 ℃ （ 13－ 7）／ ＝ e 29→24 ℃ 26←21 ℃ （ 26－ 21）／ 3＝ plate heat exchanger and NTUE NTUE plate heat exchanger that the capacity of heat exchanger is the size of a certain length of the heat and the bination of heat transfer units, the total length of heat transfer process is the length and number of units of the product. When the total number of NTUE is, if the number of processes for every 1 NTUe, then NTUE = n • NTUe (where n is the nu。