Heat Transfer Equipment - Revision history

Btm295: /* Example Problem Solution */

2015-03-14T04:19:28Z

Example Problem Solution

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	these velocities are slightly out of the design range of 1-2 feet per second, and are therefore reasonable but not recommended for design.		these velocities are slightly out of the design range of 1-2 feet per second, and are therefore reasonable but not recommended for design.


	'''Aside: Simulation Environments to aid in plate-heat exchanger design'''		'''Aside: Simulation Environments to aid in plate-heat exchanger design'''

Btm295: /* Example Problem Solution */

2015-03-14T04:19:09Z

Example Problem Solution

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	these velocities are slightly out of the design range of 1-2 feet per second, and are therefore reasonable but not recommended for design.		these velocities are slightly out of the design range of 1-2 feet per second, and are therefore reasonable but not recommended for design.

	Aside: Simulation Environments to aid in plate-heat exchanger design		'''Aside: Simulation Environments to aid in plate-heat exchanger design'''

	There are many different factors to consider when designing a plate heat exchanger. In the example problem, a few easy-to-calculate parameters were chosen. In practical application, there are several simulation packages available to aid aid in design and make designs more accurate. Aspen has design software available (developers of HYSYS) that allows for performance simulation of gasketed, welded, and brazed heat exchangers. It also can provide optimum heat exchanger configuration. (AspenTech, 2015) Xphe also has a simulation package available that allows for heat exchanger design and analysis. It also allows for different chevron angles to be specified, as well as non-newtonian fluids. (HTRI, 2015) Both programs have an extensive bank of fluids and the ability to specify an original fluid not in memory.		There are many different factors to consider when designing a plate heat exchanger. In the example problem, a few easy-to-calculate parameters were chosen. In practical application, there are several simulation packages available to aid aid in design and make designs more accurate. Aspen has design software available (developers of HYSYS) that allows for performance simulation of gasketed, welded, and brazed heat exchangers. It also can provide optimum heat exchanger configuration. (AspenTech, 2015) Xphe also has a simulation package available that allows for heat exchanger design and analysis. It also allows for different chevron angles to be specified, as well as non-newtonian fluids. (HTRI, 2015) Both programs have an extensive bank of fluids and the ability to specify an original fluid not in memory.

Btm295 at 04:18, 14 March 2015

2015-03-14T04:18:29Z

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	Finally, chevron arrangement affects heat transfer. Each manufacturer configures corrugation patterns differently, with some companies offering multiple styles. In general, however, increasing the chevron angle decreases the heat transfer and the pressure drop. Therefore, altering chevron angle is another way use the trade off between heat transfer and pressure drop limitations. For the two plates shown on the right, the left plate has a high angle, and therefore higher heat transfer and higher pressure drop. Unfortunately, each company has a specific, proprietary arrangement and design of corrugation (Towler and Sinnott, 2013).		Finally, chevron arrangement affects heat transfer. Each manufacturer configures corrugation patterns differently, with some companies offering multiple styles. In general, however, increasing the chevron angle decreases the heat transfer and the pressure drop. Therefore, altering chevron angle is another way use the trade off between heat transfer and pressure drop limitations. For the two plates shown on the right, the left plate has a high angle, and therefore higher heat transfer and higher pressure drop. Unfortunately, each company has a specific, proprietary arrangement and design of corrugation (Towler and Sinnott, 2013).

	~~'''Simulation Environments for Exchanger Design'''~~

	As seen above, there are many different factors to consider when designing a plate heat exchanger. To aid in design, there are several simulation packages available. Aspen has design software available (developers of HYSYS) that allows for performance simulation of gasketed, welded, and brazed heat exchangers. It also can provide optimum heat exchanger configuration. (AspenTech, 2015) Xphe also has a simulation package available that allows for heat exchanger design and analysis. It also allows for different chevron angles to be specified, as well as non-newtonian fluids. (HTRI, 2015) Both programs have an extensive bank of fluids and the ability to specify an original fluid not in memory.

	===Gas-to-Gas===		===Gas-to-Gas===
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	Note: Assume <math>p_h=1000</math> <math>\frac{kg}{m^3}</math> and <math>p_c=900</math> <math>\frac{kg}{m^3}</math> at T_avg.		Note: Assume <math>p_h=1000</math> <math>\frac{kg}{m^3}</math> and <math>p_c=900</math> <math>\frac{kg}{m^3}</math> at T_avg.

	=Example Problem 1 Solution=		=Example Problem Solution=
			Part a.
	We are trying to solve for two things in this problem: the '''outlet temperature of the cold stream <math>T_{c,out}</math>''' and the '''heat-exchange area <math>A</math>'''. In order to find the outlet temperature <math>T_{c,out}</math>, we need to find the total heat transfer rate, which is equal to the amount of energy lost by the hot stream. The amount of energy gained by the cold stream is the opposite of this value. The absolute value of either will give the heat duty <math>Q</math>We can then relate the energy change to the temperature change using the heat capacity and mass flow rate.		We are trying to solve for two things in this problem: the '''outlet temperature of the cold stream <math>T_{c,out}</math>''' and the '''heat-exchange area <math>A</math>'''. In order to find the outlet temperature <math>T_{c,out}</math>, we need to find the total heat transfer rate, which is equal to the amount of energy lost by the hot stream. The amount of energy gained by the cold stream is the opposite of this value. The absolute value of either will give the heat duty <math>Q</math>We can then relate the energy change to the temperature change using the heat capacity and mass flow rate.

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	From this we are able to obtain <math>A=41.58 m^2</math>		From this we are able to obtain <math>A=41.58 m^2</math>

	~~=Example Problem 2 Solution=~~		Part b.
	~~First~~, include a 10% design factor~~, so~~ design area, <math>DA=1.10*A=45.73m^2</math>		Using the area from part a, include a 10% design factor to obtain design area, DA.

			<math>DA=1.10*A=45.73m^2</math>

	Next determine the size of each plate. From literature, we find that each plate has a heat transfer area of 0.24 m<sup>2</sup>, and dimensions of 1.0 m high by 0.47 m wide.		Next determine the size of each plate. From literature, we find that each plate has a heat transfer area of 0.24 m<sup>2</sup>, and dimensions of 1.0 m high by 0.47 m wide.
	Divide design area by area per plate to determine number of plates, N.		Divide design area by area per plate to determine number of plates, N.
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	these velocities are slightly out of the design range of 1-2 feet per second, and are therefore reasonable but not recommended for design.		these velocities are slightly out of the design range of 1-2 feet per second, and are therefore reasonable but not recommended for design.

			Aside: Simulation Environments to aid in plate-heat exchanger design

			There are many different factors to consider when designing a plate heat exchanger. In the example problem, a few easy-to-calculate parameters were chosen. In practical application, there are several simulation packages available to aid aid in design and make designs more accurate. Aspen has design software available (developers of HYSYS) that allows for performance simulation of gasketed, welded, and brazed heat exchangers. It also can provide optimum heat exchanger configuration. (AspenTech, 2015) Xphe also has a simulation package available that allows for heat exchanger design and analysis. It also allows for different chevron angles to be specified, as well as non-newtonian fluids. (HTRI, 2015) Both programs have an extensive bank of fluids and the ability to specify an original fluid not in memory.

	=Conclusions=		=Conclusions=

Btm295: /* Example Problem 1 */

2015-03-14T04:14:14Z

Example Problem 1

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	If a plate-heat exchanger were used with the same area, determine the necessary number of plates for heat transfer and ensure that the channel velocities are acceptable.		If a plate-heat exchanger were used with the same area, determine the necessary number of plates for heat transfer and ensure that the channel velocities are acceptable.
	Use an M10-M plate heat exchanger, with a maximum heat transfer area of 90 m<sup>2</sup>.		Use an M10-M plate heat exchanger, with a maximum heat transfer area of 90 m<sup>2</sup>.

	Note: Assume <math>p_h=1000</math> <math>\frac{kg}{m^3}</math> and <math>p_c=900</math> <math>\frac{kg}{m^3}</math> at T_avg.		Note: Assume <math>p_h=1000</math> <math>\frac{kg}{m^3}</math> and <math>p_c=900</math> <math>\frac{kg}{m^3}</math> at T_avg.

Btm295: /* Example Problem 1 */

2015-03-14T04:13:48Z

Example Problem 1

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	=Example Problem 1=		=Example Problem 1=
			Part a.
	A stream of hot fluid at <math>T_{h, in}=120 ^oC</math> flowing at <math>\dot{m_h}=10 \frac{kg}{s}</math> needs to be cooled to <math>T_{c,out}=60 ^oC</math>. Its heat capacity is <math>C_{p,h}2=\frac{kJ}{kg\cdot^oC}</math>. A cold stream at <math>\dot{m_c}=8 \frac{kg}{s}</math> and <math>T_{c,in}=50 ^oC</math> is available to cool it. The heat capacity of the old stream is <math>C_{p,c}=3 \frac{kJ}{kg\cdot^oC}</math>. If they are contacted in a true counter current pattern in a double tube heat exchanger with overall heat-transfer coefficient <math>U = 2\frac{kJ}{m^2\cdot^oC\cdot s}</math>, what is the outlet temperature of the cold stream, and what is the area A needed for this heat exchange rate?		A stream of hot fluid at <math>T_{h, in}=120 ^oC</math> flowing at <math>\dot{m_h}=10 \frac{kg}{s}</math> needs to be cooled to <math>T_{c,out}=60 ^oC</math>. Its heat capacity is <math>C_{p,h}2=\frac{kJ}{kg\cdot^oC}</math>. A cold stream at <math>\dot{m_c}=8 \frac{kg}{s}</math> and <math>T_{c,in}=50 ^oC</math> is available to cool it. The heat capacity of the old stream is <math>C_{p,c}=3 \frac{kJ}{kg\cdot^oC}</math>. If they are contacted in a true counter current pattern in a double tube heat exchanger with overall heat-transfer coefficient <math>U = 2\frac{kJ}{m^2\cdot^oC\cdot s}</math>, what is the outlet temperature of the cold stream, and what is the area A needed for this heat exchange rate?

	~~Consequently, if~~ a plate-heat exchanger were used with the same area, determine the necessary number of plates for heat transfer and ensure that the channel velocities are acceptable.		Part b.
			If a plate-heat exchanger were used with the same area, determine the necessary number of plates for heat transfer and ensure that the channel velocities are acceptable.
			Use an M10-M plate heat exchanger, with a maximum heat transfer area of 90 m<sup>2</sup>.
			Note: Assume <math>p_h=1000</math> <math>\frac{kg}{m^3}</math> and <math>p_c=900</math> <math>\frac{kg}{m^3}</math> at T_avg.

	=Example Problem 1 Solution=		=Example Problem 1 Solution=

Btm295: /* Example Problem 2 */

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Example Problem 2

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	From this we are able to obtain <math>A=41.58 m^2</math>		From this we are able to obtain <math>A=41.58 m^2</math>

	~~=Example Problem 2=~~
	~~From the area calculated in Example Problem 1, determine the number of plates and channel velocities for a plate-and-frame heat exchanger. Are these numbers reasonable?~~
	~~Use an M10-M plate heat exchanger, with a maximum heat transfer area of 90 m<sup>2</sup>.~~
	~~Assume <math>p_h=1000</math> <math>\frac{kg}{m^3}</math> and <math>p_c=900</math> <math>\frac{kg}{m^3}</math> at T_avg.~~

	=Example Problem 2 Solution=		=Example Problem 2 Solution=

Btm295: /* Example Problem 1 */

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Example Problem 1

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	=Example Problem 1=		=Example Problem 1=
	A stream of hot fluid at <math>T_{h, in}=120 ^oC</math> flowing at <math>\dot{m_h}=10 \frac{kg}{s}</math> needs to be cooled to <math>T_{c,out}=60 ^oC</math>. Its heat capacity is <math>C_{p,h}2=\frac{kJ}{kg\cdot^oC}</math>. A cold stream at <math>\dot{m_c}=8 \frac{kg}{s}</math> and <math>T_{c,in}=50 ^oC</math> is available to cool it. The heat capacity of the old stream is <math>C_{p,c}=3 \frac{kJ}{kg\cdot^oC}</math>. If they are contacted in a true counter current pattern in a double tube heat exchanger with overall heat-transfer coefficient <math>U = 2\frac{kJ}{m^2\cdot^oC\cdot s}</math>, what is the outlet temperature of the cold stream, and what is the area A needed for this heat exchange rate?		A stream of hot fluid at <math>T_{h, in}=120 ^oC</math> flowing at <math>\dot{m_h}=10 \frac{kg}{s}</math> needs to be cooled to <math>T_{c,out}=60 ^oC</math>. Its heat capacity is <math>C_{p,h}2=\frac{kJ}{kg\cdot^oC}</math>. A cold stream at <math>\dot{m_c}=8 \frac{kg}{s}</math> and <math>T_{c,in}=50 ^oC</math> is available to cool it. The heat capacity of the old stream is <math>C_{p,c}=3 \frac{kJ}{kg\cdot^oC}</math>. If they are contacted in a true counter current pattern in a double tube heat exchanger with overall heat-transfer coefficient <math>U = 2\frac{kJ}{m^2\cdot^oC\cdot s}</math>, what is the outlet temperature of the cold stream, and what is the area A needed for this heat exchange rate?

			Consequently, if a plate-heat exchanger were used with the same area, determine the necessary number of plates for heat transfer and ensure that the channel velocities are acceptable.

	=Example Problem 1 Solution=		=Example Problem 1 Solution=

Btm295 at 04:10, 14 March 2015

2015-03-14T04:10:35Z

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	Channel velocities are important to reduce fouling between plates. Since there is a small gap between plates, a small amount of fouling can significantly reduce heat transfer. Although increasing plate gap can lengthen the amount of time between cleanings, increasing channel velocity allows a small gap to be retained, while still increasing time between cleanings. However, channel velocities that are too high can increase the risk for a blowout. For most design applications, 1-2 ft/s allow for reduced fouling while ensuring safe operation (Peters et al., 2002).		Channel velocities are important to reduce fouling between plates. Since there is a small gap between plates, a small amount of fouling can significantly reduce heat transfer. Although increasing plate gap can lengthen the amount of time between cleanings, increasing channel velocity allows a small gap to be retained, while still increasing time between cleanings. However, channel velocities that are too high can increase the risk for a blowout. For most design applications, 1-2 ft/s allow for reduced fouling while ensuring safe operation (Peters et al., 2002).

	[[File:PlatePatterns.jpg\|right~~\|250px~~]]		[[File:PlatePatterns.jpg\|thumb\|Example of a high-theta plate (left) and a low-theta plate (right)]]

	Plate gap is exactly as it sounds - the gap between two plates. Typical gaps between plates range from 1.3 - 1.5 mm. Increasing the gap between plates reduces velocity and decreases pressure drop, but decreases heat transfer as there is more fluid that does not contact either side of the plate. Plate gap can be adjusted in industry by tightening or loosening the end bolts on the heat exchanger - although overtightening can lead to crushing, and undertightening can result in leaks.		Plate gap is exactly as it sounds - the gap between two plates. Typical gaps between plates range from 1.3 - 1.5 mm. Increasing the gap between plates reduces velocity and decreases pressure drop, but decreases heat transfer as there is more fluid that does not contact either side of the plate. Plate gap can be adjusted in industry by tightening or loosening the end bolts on the heat exchanger - although overtightening can lead to crushing, and undertightening can result in leaks.

Btm295 at 03:59, 14 March 2015

2015-03-14T03:59:27Z

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	'''Simulation Environments for Exchanger Design'''		'''Simulation Environments for Exchanger Design'''

	As seen above, there are many different factors to consider when designing a plate heat exchanger. To aid in design, there are several simulation packages available. Aspen has design software available (developers of HYSYS) that allows for performance simulation of gasketed, welded, and brazed heat exchangers. It also can provide optimum heat exchanger configuration. Xphe also has a simulation package available that allows for heat exchanger design and analysis. It also allows for different chevron angles to be specified, as well as non-newtonian fluids. Both programs have an extensive bank of fluids and the ability to specify an original fluid not in memory.		As seen above, there are many different factors to consider when designing a plate heat exchanger. To aid in design, there are several simulation packages available. Aspen has design software available (developers of HYSYS) that allows for performance simulation of gasketed, welded, and brazed heat exchangers. It also can provide optimum heat exchanger configuration. (AspenTech, 2015) Xphe also has a simulation package available that allows for heat exchanger design and analysis. It also allows for different chevron angles to be specified, as well as non-newtonian fluids. (HTRI, 2015) Both programs have an extensive bank of fluids and the ability to specify an original fluid not in memory.

	===Gas-to-Gas===		===Gas-to-Gas===
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	Seider WD, Seader JD, Lewin DR. Process Design Principles: Synthesis, Analysis, and Evaluation. 3rd ed. New York: Wiley; 2004.		Seider WD, Seader JD, Lewin DR. Process Design Principles: Synthesis, Analysis, and Evaluation. 3rd ed. New York: Wiley; 2004.

			AspenTech. "Aspen Exchanger Design & Rating (EDR)." AspenTech. Web. Mar. 2015.

			HTRI. "Xphe." Heat Transfer Research, Inc. N.p., n.d. Web. 13 Mar. 2015.

Btm295: /* Example Problem 2 Solution */

2015-03-14T03:45:51Z

Example Problem 2 Solution

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	We determine that the channel velocities are as follows:		We determine that the channel velocities are as follows:

	<math>v_{ch,h}=\frac{0.01\frac{m^3}{s}}{A_c}=~~142~~\frac{m}{s}</math> and <math>v_{ch,c}=\frac{8.89*10^{-3}\frac{m^3}{s}}{A_c}=~~126~~\frac{m}{s}</math>		<math>v_{ch,h}=\frac{0.01\frac{m^3}{s}}{CA_c}=1.56\frac{m}{s}</math> and <math>v_{ch,c}=\frac{8.8910^{-3}\frac{m^3}{s}}{C*A_c}=1.38\frac{m}{s}</math>

	these velocities ~~greatly exceed~~ the design ~~values~~ of 1-2 feet per second, and are therefore ~~unreasonable~~.		these velocities are slightly out of the design range of 1-2 feet per second, and are therefore reasonable but not recommended for design.

	=Conclusions=		=Conclusions=