Parallel Flow And Counterflow Heat Exchanger Pdf

parallel flow and counterflow heat exchanger pdf

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Parallel And Counter Flow Heat Exchanger Pdf

Burlingame, California, USA. July 16—18, The transient and steady-state response of single pass constant-flow concentric parallel flow, concentric counter flow heat exchangers was investigated using a finite volume method. Heat exchanger transients initiated by both step-change and sinusoidally varying hot stream inlet temperatures were investigated. The wall separating the fluid streams was modeled by conduction with thermal mass; hence the heat exchanger transient behavior is dependent on the thermal mass of the fluid streams as well as the internal wall. The outer wall is approximated as fully insulating. The time dependent temperature profiles were investigated as a function of heat exchanger dimensionless length and dimensionless time for both fluids.

In heat exchanger analysis, if the fluid inlet and outlet temperatures are specified or can be determined by simple energy balance, the LMTD method can be used; but when these temperatures are not available The NTU or The Effectiveness method is used. The effectiveness-NTU method is very useful for all the flow arrangements besides parallel flow and counterflow ones because the effectiveness of all other types must be obtained by a numerical solution of the partial differential equations and there is no analytical equation for LMTD or effectiveness, but as a function of two variables the effectiveness for each type can be presented in a single diagram. To define the effectiveness of a heat exchanger we need to find the maximum possible heat transfer that can be hypothetically achieved in a counter-flow heat exchanger of infinite length. The method proceeds by calculating the heat capacity rates i. The other fluid would change temperature more slowly along the heat exchanger length. The method, at this point, is concerned only with the fluid undergoing the maximum temperature change.

NTU method

It is common knowledge amongst heat exchanger designers that a counter flow heat exchanger installation is more efficient than the parallel flow alternative, but for everyone else it can be a bit of a mystery. In this article we will explain what counter flow is and why it is more efficient than parallel flow. First we need to understand what the differences are between counter flow and parallel flow. As a brief description; the term refers to the relationship between the flow directions of the hot and cold fluids. With parallel flow the fluids are travelling through the heat exchanger in the same direction where as a counter flow installation will have the fluids flowing against each other in opposite directions. The diagram above shows a Shell and Tube Heat Exchanger.

This is an interesting question. Let's see if we can visualize this a bit better. Let's take the case when we want to extract the maximum amount of heat from a given hot stream. What design should we adopt? The figure below depicts heat exchanger.

Heat exchangers are typically classified according to flow arrangement and type of construction. The simplest heat exchanger is one for which the hot and cold fluids move in the same or opposite directions in a concentric tube or double-pipe construction. Figure The two configurations differ according to whether the fluid moving over the tubes is unmixed or mixed. In this case the fluid temperature varies with and. Since the tube flow is unmixed, both fluids are unmixed in the finned exchanger, while one fluid is mixed and the other unmixed in the unfinned exchanger.

Heat exchanger description. 2. Parallel flow heat exchangers. 3. Counter flow heat exchangers. 4. Effectiveness. 5. NTU. 6. Phase Change. 7. Constant specific​.

Heat Exchangers

Sridharan, M. October 15, Thermal Sci. June ; 12 3 : The heat exchanger is a device in which heat transfer takes place between two fluids at different temperatures.

Sridharan, M. October 15, Thermal Sci.

Heat Transfer pp Cite as. Thus far, we have been concerned with heat transfer phenomena. In this chapter, we are concerned with types of equipment that are intended to accomplish the transfer of heat. General classes of heat exchangers are described, as are general considerations of heat exchanger design.

Heat Exchangers

Why counter flow heat exchangers are more efficient

The most common arrangements for flow paths within a heat exchanger are counter-flow and parallel flow. A counter-flow heat exchanger is one in which the direction of the flow of one of the working fluids is opposite to the direction to the flow of the other fluid. In a parallel flow exchanger, both fluids in the heat exchanger flow in the same direction.

Heat exchangers are typically classified according to flow arrangement and type of construction. The simplest heat exchanger is one for which the hot and cold fluids move in the same or opposite directions. This heat exchanger consists of two concentric pipes of different diameters. Figure represents the directions of fluid flow in the parallel and counter-flow exchangers. Under comparable conditions, more heat is transferred in a counter-flow arrangement than in a parallel flow heat exchanger. The temperature profiles of the two heat exchangers indicate two major disadvantages in the parallel-flow design. The design of a parallel flow heat exchanger is advantageous when two fluids are required to be brought to nearly the same temperature.

 Неужели? - Стратмор по-прежнему оставался невозмутим.  - Что показалось тебе странным. Сьюзан восхитилась спектаклем, который на ее глазах разыгрывал коммандер. - ТРАНСТЕКСТ работает с чем-то очень сложным, фильтры никогда ни с чем подобным не сталкивались. Боюсь, что в ТРАНСТЕКСТЕ завелся какой-то неизвестный вирус. - Вирус? - снисходительно хмыкнул Стратмор, - Фил, я высоко ценю твою бдительность, очень высоко.

PDF | Heat exchangers are used widely in many industries for heat recovery or cooling purposes. This paper developed a numerical model to simulate a | Find​.

Why counter flow heat exchangers are more efficient

 Семьдесят четыре и восемь десятых, - сказала Сьюзан.  - Но я не думаю… - С дороги! - закричал Джабба, рванувшись к клавиатуре монитора.  - Это и есть ключ к шифру-убийце. Разница между критическими массами. Семьдесят четыре и восемь десятых.

ГЛАВА 40 Стоя у двери Третьего узла, Чатрукьян с безумным видом отчаянно пытался убедить Хейла в том, что с ТРАНСТЕКСТОМ стряслась беда. Сьюзан пробежала мимо них с одной только мыслью - как можно скорее предупредить Стратмора. Сотрудник лаборатории систем безопасности схватил ее за руку.

Ничего более абсурдного Сьюзан слышать еще не доводилось. Цифровая крепость - не поддающийся взлому код, он погубит агентство.

 - Он прикусил губу.  - Шифр, над которым работает ТРАНСТЕКСТ, уникален. Ни с чем подобным мы еще не сталкивались.

 - Откроем пачку тофу. - Нет, спасибо.  - Сьюзан шумно выдохнула и повернулась к.  - Я думаю, - начала она, -что я только… -но слова застряли у нее в горле.

Он был бледен и еле дышал. Увидев тело Хейла, Стратмор вздрогнул от ужаса. - О Боже! - воскликнул.  - Что случилось. ГЛАВА 93 Причастие.

Простыня на его половине кровати была холодной. Дэвид исчез. Значит, приснилось, подумала Сьюзан и села в кровати.