A tubular heat exchanger, also known as a shell and tube heat exchanger, is a wall to wall heat exchanger with the wall of the tube bundle enclosed in the shell as the heat transfer surface. This type of heat exchanger can be made of various structural materials (mainly metal materials) and can be used under high temperature and high pressure. It has a simple structure, low cost, wide flow cross-section, and is easy to clean scale.
According to their types, they can be divided into fixed tube sheet tube heat exchangers, floating head tube heat exchangers, packed box tube heat exchangers, U-shaped tube tube heat exchangers, eddy current film tube heat exchangers, baffle tube heat exchangers, and multi shell tube heat exchangers.

A tubular heat exchanger consists of a shell, heat transfer tube bundle, tube sheet, baffle (baffle), and tube box. The shell is mostly cylindrical, with a tube bundle inside, and the two ends of the tube bundle are fixed on the tube plate. Two types of fluids, hot and cold, are used for heat exchange. One flows inside the tube and is called the tube side fluid; Another type of fluid that flows outside the tube is called shell side fluid.
To improve the heat transfer coefficient of the fluid outside the pipe, several baffles are usually installed inside the shell. The baffle can increase the velocity of the shell side fluid, forcing the fluid to pass through the bundle laterally multiple times according to the specified path, and enhancing the degree of fluid turbulence. The heat exchange tubes can be arranged in equilateral triangles or squares on the tube plate. The equilateral triangle arrangement is relatively compact, resulting in high turbulence of the fluid outside the tube and a large heat transfer coefficient; Square arrangement makes cleaning outside the tube convenient and suitable for fluids that are prone to scaling.
Each time a fluid passes through a tube bundle is called a tube pass; Each pass through the shell is called a shell pass. To increase the fluid velocity inside the pipe, partitions can be installed inside both ends of the pipe box to divide all pipes into several groups. This way, the fluid only passes through a portion of the tubes at a time, so it travels back and forth multiple times in the bundle, which is called multi tube pass. Similarly, to increase the flow velocity outside the pipe, longitudinal baffles can also be installed inside the shell to force the fluid to pass through the shell space multiple times, known as multi shell pass. Multi tube and multi shell can be used in conjunction.

Nominal Diameter	Number of tubes	Number of pipes	Heat Exchange Area Nominal value/calculated value					Cross sectional area of pipeline channel Flow rate at a flow rate of 0.5m/sec in the pipeline channel m/hr		Nominal pressure
			Pipe length (m)					φ25×2.5
			1500	2000	3000	4000	6000	φ25×2
159	Ⅰ	14	1.51.62	22.17	33.27			0.0044/ 0.0049	7.92/ 8.82	0.25
219	Ⅰ	26	3/3.00	4/4.02	6/6.06	8/8.1		0.0082/ 0.0090	14.76/ 16.20	0.6
	Ⅱ	26	3/3.00	4/4.02	6/6.06	8/8.81		0.0041/ 0.0045	7.38/ 8.01	1.0
273	Ⅰ	44	5/5.08	7/5.18	10/10.26	14/13.72	21/20.63	0.0138/ 0.0152	24.84/ 27.36	1.6
	Ⅱ	40	5/4.62	6/6.19	9/9.33	12/12.47	19/18.76	0.0063/ 0.0069	11.24/ 12.42	2.5
325	Ⅰ	60	7/6.93	9/9.28	14/14.00	19/18.71	28/28.13	0.0188/ 0.0208	33.84/ 37.44	0.6
	Ⅱ	56	6/6.47	9/8.66	13/13.05	17/17.46	36/26.26	0.0088/ 0.0097	15.84/ 17.46	1.0
400	Ⅰ	119	14/13.47	18/18.41	28/27.76	37/37.10	55/55.8	0.0374/ 0.0412	67.32/ 74.16	1.6
	Ⅱ	110	13/12.70	17/17.02	26/25.66	34/34.20	50/51.58	0.0173/ 0.0190	31.14/ 34.20	2.5
500	Ⅰ	185			45/4.15	55/57.68	85/86.74	0.0581/ 0.0641	104.58/ 115.38
	Ⅱ	180			40/41.99	55/57.68	85/86.74	0.0283/ 0.0312	50.94/ 56.16
600	Ⅰ	269			60/62.7	85/83.88	125/126.13	0.0845/ 0.0932	152.10/ 167.76
	Ⅱ	266			60/32.05	80/82.94	125/14.72	0.0418/ 0.0461	75.24/ 83.98
700	Ⅰ	379			90/88.41	120/118.17	175/177.71	0.0091/ 0.1313	214.38/ 236.34
	Ⅱ	358			85/83.51	110/111.62	165/167.85	0.0562/ 0.0620	101.16/ 111.60
800	Ⅰ	511			120/119.20	160/159.16	240/239.60	0.1605/ 0.1770	288.90/ 318.60
	Ⅱ	488			115/113.83	150/152.16	230/228.81	0.0767/ 0.0845	138.06/ 152.10
900	Ⅰ	649			150/151.39	200/202.36	305/304.3	0.2039/ 0.2248	367.02/ 404.46
	Ⅱ	630			145/146.96	195/196.44	295/295.40	0.0990/ 0.1091	178.20/ 196.38
1000	Ⅰ	805			185/187.78	250/251.00	375/377.45	0.2529/ 0.2788	455.22/ 501.74
	Ⅱ	792			185/184.75	245/246.95	370/371.36	0.1244/ 0.1374	223.92/ 246.96