201007114 六、發明說明： 【福^月所屬冬好々真】 發明領域 本文揭露的實施例係大體關於—種熱交換器。較特定 地’本文揭露的實施例係關於一種配置成有效地處理二相 流的熱交換器’諸如一殼管式熱交換器。201007114 VI. Description of the Invention: [Future of the Year of the Year] Field of the Invention The embodiments disclosed herein relate generally to heat exchangers. More specifically, the embodiments disclosed herein relate to a heat exchanger such as a shell and tube heat exchanger configured to efficiently treat a two-phase flow.
I：先前技術J 發明背景 © 熱交換器的許多配置是習知的且被用於種種應用中。 該等廣泛使用的配置之一，一殼管式熱交換器，如第丨圖所 示，包括罩蓋一東平行管12的一圓柱殼1〇，該等平行管12 - 在兩個端板14之間延伸使得一第一流體丨6可通過該等管 - 12。同時’一第二流體18流入且通過該等兩個端板之間的 空間以與該等管接觸。爲了在兩個流體之間提供一改進的 熱交換，第二流體18的流徑由形成個別通道的中間擋板2〇 界定，該等擋板被安排成使得第二流體在通過一個通道到 ® 達下一個通道時改變其方向。擋板20被配置為如圖所示的 部份圓弧形(部份扇形擋板），或被配置為孔環或圓盤，係垂 直於殼10的一縱軸22被安裝以提供第二流體18的一曲折流 動24。 在此安排中，該第二流體必須沿該殼之長度急遽改變 其流動方向數次。這導致該第二流體的動壓力及其非均速 流動速度的降低，其合併不利地影響該熱交換器的性能。 例如’該等擋板相對殼之縱轴的一垂直位置導致一相對效 201007114 率低的傳熱率/壓降比。另外，該種擋板安排造成通過擋板 與殼及管與擋板間隙的流量旁通，除其他不希望的後果之 外，導致流量不良分佈、渦流、回流及較高的積垢速度。 壓降、流量分佈，及熱傳遞效率是重要的變數，尤其 在液相饋入物與產品流之間需要一氣相反應的許多工業化 學方法中。範例方法可包括石油腦重組、石油腦氫化處理、 柴油與煤油氫化處理、輕烴異構化作用及複分解，及許多 其他工業上重要的方法。此種方法將典型地包括饋入物/排 出物熱交換設備，其中蒸發該反應器饋入流所需要的熱量 由該反應器排出物的冷凝物或部份冷凝物重新獲得。該種 熱傳遞設備在歷史上被安排為習知的水平殼管式熱交換 器。 增加單元設計容量（規模經濟）需要大容積通過料量，故 對以有限溫差傳遞熱量所需要的殼數目產生影響。然而， 由於水流水力學上的問題，即，兩相輸入流，氣相及液相 的多樣化組成及分子量，及由相變導致的可變容積流量及 壓降，並聯及_聯配置的習知的交換器配置是有疑問的。 對稱的配管在實現分開兩相流上是一種不可靠的方法。因 為蒸汽分子量可遠低於相關聯的液體，尤其在蒸汽大部份 由氫組成的氫化處理服務中，蒸汽不良分佈隨以液體進入 一交換器對相關聯的沸騰曲線及因此對該沸騰操作的平均 溫差(MTD)有顯著影響。 垂直組合式饋入物/排出物熱交換器（VCFE)的概念被 開發以藉由將大平面整合為一單一垂直殼克服該等缺點。 201007114 此等單元已以不同的結構被商業化配置，該等結構包括： 單一扇形檔板設計的管侧沸騰/殼側冷凝；單一扇形擋板設 計的管側冷凝/殼側沸騰；螺旋擋板設計的管側沸騰/殼側冷 凝；螺旋擋板設計的管側冷凝/殼側沸騰。螺旋擋板交換器 在例如美國專利第5,832,991號案、第6,513,583號案及第 6,827,138號案中被描述。 在一理論基礎上，殼側彿騰有助於減少所需平面，因 為殼側沸騰係數由於質傳效應而藉由相對較大的殼側體積 ® 被增加。然而，積垢問題必須也被處理，因為管側通常會 較易於清潔。 殼侧沸騰安排的一個缺點在部份負載或調減操作上被 " 考慮，其中該殼側速度可能不足以防止相分離及液體部份 ' 回流到入口。這種高滯留時間的重液部份的累積可導致積 垢。 任一管側沸騰配置的主要缺點是蒸汽及液體部份必須 均勻分佈在各該多數管入口中，以維持各管中希望的彿騰 特徵’且一種實現該分佈的低廉且低壓降方法還未被發現。 因此，對可供在垂直單元中有效處理兩相輸入流的熱 交換器及擋板設計存有需求。 【發明内容】 發明概要 在一個層面，本文揭露的實施例係關於一種熱交換 器，該熱交換器包括：一具有一流體入口及一流體出口之 殼；被安裝於該殼中以引導該流體成_螺旋流型通過該殼 201007114 的複數擋板；其中接近該入口的一擒板的一螺旋角α不同於 接近該出口的一擋板的一螺旋角β。 在另一層面，本文揭露的實施例係關教—種殼管式熱 交換器，該殼管式熱交換器包括：一管侧入口歧管，其中 具有一第一流體入口； 一管側出口歧管，其中具有一第一 流體出口；複數管，在該等歧管之間延伸且與該等歧管流 體連通；一殼，在該等歧管之間延伸且包圍該等管，該殼 中具有一第二流體入口及一第二流體出口；複數擋板，被 安裝於該殼中以引導該第二流體成一螺旋流型通過該殼； ❹ 其中接近該第二流體入口的一擋板的一螺旋角α不同於接 近該第二流體出口的一擋板的一螺旋角β。 在另一層面，本文揭露的實施例係關於一種以一混合 — 相流體熱交換的方法，該方法包括：將一包含一蒸汽及一 ‘ 夾帶流體與一夾帶固體中至少一者的混合相流體饋入一熱 交換器，該熱交換器包括：一殼，具有一流體入口及一流 體出口；複數擋板，被安裝於該殼中以引導該流體成一螺 旋流型通過該殼；將該混合相流體轉換成實質上皆為蒸 ’ 汽；且在該混合相流體與一熱交換媒體之間間接熱交換； 其中接近該入口的一擋板的一螺旋角α維持該混合相流體 的速度大於該夾帶流體或固體的一終速度；且其中接近該 出口的一擋板的一螺旋角β大於接近該入口的該擋板的螺 旋角α。 其他層面及優勢由下文描述及所附申請專利範圍將是 明顯的。 6 201007114 圖式簡單說明 第1圖是％示在一習知殼管式熱交換器中的流體分佈 的示意圖。 第2圖是繪示依據本文所揭露的實施例具可變熱擋板 角度的一垂直钽合式饋入物/排出物熱交換器的示意圖。 【實施*冷式】 較佳實施例之詳細說明 在一個層面，本文的實施例係大體關於一種熱交換 β 器。較特定地，本文揭露的實施例係關於一種被配置成可 有效地處理二相流的熱交換器’諸如一殼管式熱交換器。 更加特定地，本文揭露的實施例係關於一種具有擋板被配 ' 置成引導一殼侧流體成一螺旋流型的熱交換器，其中一接 ' 近入口的擋板的一螺旋角不同於一接近出口的擋板的一螺 旋角。 依據本文揭露的實施例’檔板具有一變化螺旋角的熱 交換器已被發現可利用於經歷一相變諸如蒸發、冷凝、燃 ® 燒等等的殼側流體。例如，對於一兩相輸入流，諸如一汽 化液-汽混合物，接近入口的螺旋角可被提供以維持足夠的 流動速度以避免該蒸汽與液體的相分離。接近殼侧流體入 口的擋板螺旋角可接近一垂直於該等管的位置’因此使進 入的稠密液體以一高速旋轉。因該液體由於交換器中的熱 傳遞而蒸發’該等擋板的螺旋角離垂直較遠’諸如對於接 近殼側出口的擋板而言，對密度較低蒸汽提供較低速度熱 交換及一通過該熱交換器的一相對低壓降。 7 201007114 因為相分離（汽-液、汽-固等等）是相對密度、微粒及/ 或液滴的大小，及氣相速度的一函數，依據本文揭露的實 施例’具有一變化螺旋角之擋板的熱交換器在相同的產量 下未遭受殼側相分離，而在一具有一固定擋板角度的熱交 換器中可能會發生該殼側相分離。因此，依據本文揭露實 施例具有一變化螺旋角之擋板的熱交換器可以在顯著減少 通過料量水平下被使用’因此避免在部份負載或調減操作 下之垂直熱交換器典型相關聯的缺點。 用於接近殼側入口及出口的檔板螺旋角可取決於操作 類型。例如，對於包括一蒸汽或一汽化液體或燃燒固體的 一流體混合物而言，接近入口的擋板螺旋角可大於接近出 口的擋板螺旋角。以此方式，該兩相混合物的速度可維持 大於夾帶固體或液體的傳送速度，因此避免相分離。因該 流體蒸發或固體燃燒，一較低螺旋角可被使用。在其他實 施例中，該螺旋角可沿該殼的縱向長度逐漸減少。又例如， 對於包括要在該熱交換器中被冷凝的一蒸汽的一入口饋入 物而言，接近該殼侧入口的擋板的螺旋角可小於接近殼側 出口的擋板的螺旋角，因此增加冷凝操作期間該混合物的 速度。 現在參考第2圖，該圖為一種依據本文揭露實施例擋板 具有變化螺旋角的垂直組合式饋入物/排出物熱交換器的 示意圖。熱交換器30可包括一其中具有一流體入口 34的管 側入口歧管32。管側入口歧管32中也可具有一孔36。熱交 換器30也可包括一其中具有一流體出口 40的管側出口歧管 201007114 38在。複數管42可在管側入口歧管32與出口歧管38之間延 伸，允許一流體從入口歧管32通過管42傳送到出口歧管 38。第2圖繪示四個管的使用，然而應理解任何數量的管可 被使用。 殼44在入口與出口歧管32、38之間包圍管42延伸，且 包括一殼側流體入口 46及一殼側流體出口 48。複數擋板50 位於殼44中。擋板50例如可包括螺旋擋板，如美國專利第 5,832,991號案、第6,513,583及第6,827，138號案所述，各該 案的全部内容在此併入此文以為參考資料。擒板5〇可包括 管口（未示於圖中）以允許管42通過擋板5〇，且允許擋板50 將管42保持在一對齊的及所希望的位置。擋板5〇可引導殼 側流體成一螺旋流型通過該殼。 擋板50被配置在熱交換器30中使得接近殼側入口 46的 擋板50與接近殼側出口 48的擋板具有不同的螺旋角。該等 擂板的螺旋角例如可藉由「展開」該螺旋線，形成該螺旋 型樣的一個二維表示被決定。如第2圖所示檔板50a，該螺 旋角將接著以殼圓周C除以螺距（由一擋板弧形延伸360。橫 切的徑距）的餘切被決定。該螺距等於： P = C*tan(p); 其中β是螺旋角。因此螺旋角β等於arctan(p/C)。 如所說明的，熱交換器配備有方向垂直的螺旋擋板 5〇。接近殼側入口 46的擋板50可具有一螺旋角α。接近殼側 出口 48的擋板50具有一相對殼44之縱軸A-A的一螺旋角 β。因此，例如，對於經由殼侧入口 46進入的一汽化兩相殼 9 201007114 側饋入流而言，接近入口46的擋板50以一小螺旋角α配置； 即，比接近殼側出口 48的檔板50更接近相對轴Α-Α的垂線， 具有一螺旋角β，其中熱交換預計是一較高殼側容積流的氣 體/氣體，諸如為由於蒸發、燃燒，及/或該殼側流體加熱的 氣體/氣體。一小螺旋角α因此可使該兩相輸入流以足在一 避免相分離的速度下以一螺旋路徑旋轉。因為該殼側流體 是接近出口 48的氣體/氣體，一大於螺旋角α的螺旋角β可被 使用’因此導致一比沿殼44的整個長度使用螺旋角α為低的 壓降。 在一些實施例中，在殼側流體入口 46與出口 48中間的 擋板可具有一在螺旋角α、β之間的一螺旋角γ。例如，取決 於服務類型（例如，冷凝、蒸發等等）’擋板50的螺旋角可從 入口 46逐漸增加或減少至出口 48。在其他實施例中，擒板 50的螺旋角可經歷一個或多階改變。 如上所述，依據本文揭露的實施例擋板具有_變化螺 旋角的熱交換器可在預計有兩相流體流時使用。當預計有 兩相流時較小螺旋角可提供一較高氣相速度，避免殼側相 分離。接近入口及出口的擋板螺旋角可為該等兩相的相對 密度、固體及/或液體微粒或液滴大小（與該等微粒或液滴的 傳送速度有關）、典型饋入率、部份負載或調減饋入率、殼 側流體溫度上升及該技藝中具有通常知識者習知的其他變 數的函數。 本文所描述的垂直組合式饋入物/排出物熱交換器可 使用具有從5。到45。，包括5°到45°範圍内的一近似螺旋角的 201007114 擋板。建立一近似螺旋角的擋板角度α、β及γ的任一組合(如 果存在）可依據本文揭露的實施例被使用。 例如，在一些實施例中，螺旋角α可在從大約5。到大約 45°的範圍内；在其他實施例中在大約5。到35。的範圍内；及 在另一些其他實施例中在大約5。到25。内。 在其他實施例中，螺旋角β可在從大約15°到大約45°的 範圍内；在其他實施例中在大約25。到45。的範圍内；及在 另一些其他實施例中在大約35。到45。内。 依據本文揭露的實施例的熱交換器可有利地與具有二 或二相以上的殼側流體被使用。依據本文揭露實施例的熱 交換器諸如藉由使擋板具有一預計為兩相流之小螺旋角而 有利地提供一殼側流體流速，以最小化或避免通過該殼的 流體相分離。另外，使用預計為單相流的較大螺旋角可有 利地提供一較之於一固定螺旋角使用於整個殼時為低的壓 降。因此，與擋板具有一固定螺旋角的習知熱交換器相比， 依據本文揭露實施例的熱交換器甚至可在顯著降低通過料 量水平下維持兩相流體流，因此有利地允許一較大的通過 料量範圍。. 雖然本揭露包括一有限數量的實施例，受益於本揭露 的該技藝中具有通常知識者，將理解不違背本揭露之精神 的其他實施例可被設計。因此，該範圍應僅由所附申請專 利範圍限制。 【围式簡單説明】 第1圖是繪示在一習知殼管式熱交換器中的流體分佈 201007114 的示意圖。 第2圖是繪示依據本文所揭露的實施例具可變熱擋板 角度的一垂直組合式饋入物/排出物熱交換器的示意圖。 【主要元件符號說明】 30…熱交換器 46…殼側流體入口 32…管側入口歧管 48…殼側流體出口 34…流體入口 50、50a···擋板 36…孔 38…管側出口歧管 A-A…縱軸 C…圓周 ❿ 40…流體出口 p…螺距 42…管 44…殼 α、β、γ···螺旋角 參 12I: Prior Art J Background of the Invention © Many configurations of heat exchangers are conventional and used in a variety of applications. One of the widely used configurations, a shell-and-tube heat exchanger, as shown in the figure, includes a cylindrical shell 1〇 covering the east parallel tube 12, the parallel tubes 12 - at the two end plates The extension between 14 allows a first fluid helium 6 to pass through the tubes - 12. At the same time, a second fluid 18 flows into and through the space between the two end plates to contact the tubes. In order to provide an improved heat exchange between the two fluids, the flow path of the second fluid 18 is defined by intermediate baffles 2A forming individual channels arranged such that the second fluid passes through a passage to the ® Change the direction when you reach the next channel. The baffle 20 is configured as a partially circular arc (partial sector baffle) as shown, or as a grommet or disk mounted perpendicular to a longitudinal axis 22 of the casing 10 to provide a second A meandering flow 24 of the fluid 18. In this arrangement, the second fluid must rapidly change its flow direction several times along the length of the shell. This results in a decrease in the dynamic pressure of the second fluid and its non-average flow velocity, which combination adversely affects the performance of the heat exchanger. For example, a vertical position of the baffles relative to the longitudinal axis of the shell results in a relatively low heat transfer rate/pressure drop ratio of 201007114. In addition, the baffle arrangement causes bypass flow through the baffle and the shell and the gap between the tube and the baffle, which, among other undesirable consequences, results in poor flow distribution, eddy currents, backflow, and high fouling rates. Pressure drop, flow distribution, and heat transfer efficiency are important variables, especially in many industrial chemical processes that require a gas phase reaction between the liquid feed and the product stream. Exemplary methods may include petroleum brain recombination, petroleum brain hydrotreating, diesel and kerosene hydrogenation, light hydrocarbon isomerization and metathesis, and many other industrially important methods. Such a process will typically include a feed/exit heat exchange device wherein the heat required to evaporate the reactor feed stream is regained by condensate or partial condensate from the reactor effluent. Such heat transfer devices have historically been arranged as conventional horizontal shell and tube heat exchangers. Increasing the unit design capacity (economies of scale) requires a large volume to pass through the feed, thus affecting the number of shells required to transfer heat with a finite temperature difference. However, due to the hydraulic problems of water flow, namely, the two-phase input flow, the diversified composition and molecular weight of the gas phase and the liquid phase, and the variable volume flow and pressure drop caused by the phase change, the parallel and _ joint configuration Known switch configuration is questionable. Symmetrical piping is an unreliable method for achieving separate two-phase flow. Since the molecular weight of steam can be much lower than the associated liquid, especially in hydrotreating services where most of the steam is composed of hydrogen, the poor distribution of steam follows the boiling curve associated with the entry of liquid into an exchanger and thus the boiling operation. The mean temperature difference (MTD) has a significant effect. The concept of a vertical combined feed/discharge heat exchanger (VCFE) was developed to overcome these disadvantages by integrating the large plane into a single vertical shell. 201007114 These units have been commercialized in different configurations, including: tube side boiling/shell side condensation for a single sector baffle design; tube side condensation/shell side boiling for a single sector baffle design; Designed tube side boiling/shell side condensation; spiral side baffle design for tube side condensation/shell side boiling. A spiral baffle exchanger is described in, for example, U.S. Patent No. 5,832,991, U.S. Patent No. 6,513,583, and No. 6,827,138. On a theoretical basis, the shell side Fotten helps to reduce the required plane because the shell side boiling coefficient is increased by the relatively large shell side volume ® due to the mass transfer effect. However, the fouling problem must also be addressed as the tube side is usually easier to clean. One disadvantage of the shell side boiling arrangement is considered in the partial load or reduction operation, where the shell side speed may not be sufficient to prevent phase separation and liquid portion 'back to the inlet. Accumulation of this heavy liquid portion with a high residence time can result in fouling. The main disadvantage of either tube side boiling configuration is that the vapor and liquid portions must be evenly distributed throughout each of the tube inlets to maintain the desired Foton characteristics in each tube' and an inexpensive and low pressure drop method to achieve this distribution has not yet been be found. Therefore, there is a need for a heat exchanger and baffle design that can effectively handle two-phase input streams in a vertical unit. SUMMARY OF THE INVENTION At one level, embodiments disclosed herein relate to a heat exchanger including: a housing having a fluid inlet and a fluid outlet; mounted in the housing to direct the fluid The spiral flow pattern passes through the plurality of baffles of the shell 201007114; wherein a helix angle α of a raft close to the inlet is different from a helix angle β of a baffle near the outlet. In another aspect, the embodiments disclosed herein are teaching a shell-and-tube heat exchanger comprising: a tube side inlet manifold having a first fluid inlet therein; a tube side outlet a manifold having a first fluid outlet; a plurality of tubes extending between and in fluid communication with the manifolds; a shell extending between and surrounding the tubes, the shell Having a second fluid inlet and a second fluid outlet; a plurality of baffles mounted in the casing to direct the second fluid into a spiral flow through the casing; ❹ a baffle adjacent the second fluid inlet A helix angle α is different from a helix angle β of a baffle near the second fluid outlet. In another aspect, the embodiments disclosed herein relate to a method of heat exchange in a mixed-phase fluid, the method comprising: mixing a fluid comprising a vapor and an 'entrained fluid with at least one of an entrained solid Feeding a heat exchanger, the heat exchanger comprising: a shell having a fluid inlet and a fluid outlet; a plurality of baffles mounted in the shell to direct the fluid into a spiral flow through the shell; The phase fluid is converted to be substantially vaporized; and indirect heat exchange between the mixed phase fluid and a heat exchange medium; wherein a helix angle α of a baffle adjacent the inlet maintains the velocity of the mixed phase fluid greater than The final velocity of the entrained fluid or solid; and wherein a helix angle β of a baffle proximate the outlet is greater than a helix angle α of the baffle proximate the inlet. Other aspects and advantages will be apparent from the following description and the appended claims. 6 201007114 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing the distribution of fluid in a conventional shell and tube heat exchanger. 2 is a schematic diagram of a vertical split feed/export heat exchanger having a variable thermal baffle angle in accordance with an embodiment disclosed herein. [Implementation * Cold Mode] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT At one level, the embodiments herein relate generally to a heat exchange beta device. More specifically, the embodiments disclosed herein relate to a heat exchanger such as a shell and tube heat exchanger configured to efficiently process a two-phase flow. More particularly, the embodiments disclosed herein relate to a heat exchanger having a baffle configured to direct a shell side fluid into a spiral flow pattern, wherein a helix angle of the baffle adjacent the inlet is different from A helix angle of the baffle near the exit. Heat exchangers having a varying helix angle in accordance with the embodiments disclosed herein have been found to be useful for shell side fluids undergoing a phase change such as evaporation, condensation, combustion, and the like. For example, for a two-phase input stream, such as a vapor-liquid mixture, a helix angle near the inlet can be provided to maintain a sufficient flow rate to avoid phase separation of the vapor from the liquid. The helix angle of the baffle near the shell side fluid inlet can approach a position perpendicular to the tubes so that the incoming dense liquid is rotated at a high speed. Because the liquid evaporates due to heat transfer in the exchanger 'the helix angle of the baffles is farther from the vertical', such as for baffles near the shell side outlet, providing lower velocity heat exchange for lower density steam and one A relatively low pressure drop across the heat exchanger. 7 201007114 Since phase separation (vapor-liquid, vapor-solid, etc.) is a function of relative density, particle size and/or droplet size, and gas phase velocity, according to the embodiment disclosed herein, there is a varying helix angle. The baffle heat exchanger does not suffer from shell side phase separation at the same throughput, and the shell side phase separation may occur in a heat exchanger having a fixed baffle angle. Thus, a heat exchanger having a baffle with a varying helix angle in accordance with embodiments disclosed herein can be used to significantly reduce the amount of material passing through the throughput level - thus avoiding the typical association of vertical heat exchangers under partial load or reduction operations. Shortcomings. The flap helix angle for access to the shell side inlet and outlet may depend on the type of operation. For example, for a fluid mixture comprising a vapor or a vaporized liquid or a burning solid, the baffle helix near the inlet may be greater than the baffle helix angle near the outlet. In this way, the velocity of the two phase mixture can be maintained above the transport speed of entrained solids or liquids, thus avoiding phase separation. A lower helix angle can be used due to evaporation of the fluid or solid combustion. In other embodiments, the helix angle may gradually decrease along the longitudinal length of the shell. For another example, for an inlet feed comprising a vapor to be condensed in the heat exchanger, a helix angle of the baffle near the shell side inlet may be smaller than a helix angle of the baffle near the shell side outlet, The speed of the mixture during the condensation operation is therefore increased. Reference is now made to Fig. 2, which is a schematic illustration of a vertical combined feed/exit heat exchanger having a varying helix angle in accordance with an embodiment of the present disclosure. Heat exchanger 30 can include a tube side inlet manifold 32 having a fluid inlet 34 therein. The tube side inlet manifold 32 can also have a bore 36 therein. The heat exchanger 30 can also include a tube side outlet manifold 201007114 38 having a fluid outlet 40 therein. A plurality of tubes 42 may extend between the tube side inlet manifold 32 and the outlet manifold 38, allowing a fluid to pass from the inlet manifold 32 through the tube 42 to the outlet manifold 38. Figure 2 illustrates the use of four tubes, however it should be understood that any number of tubes can be used. The shell 44 extends around the tube 42 between the inlet and outlet manifolds 32, 38 and includes a shell side fluid inlet 46 and a shell side fluid outlet 48. A plurality of baffles 50 are located in the housing 44. The baffle 50 can, for example, include a spiral baffle as described in U.S. Patent Nos. 5,832,991, 6, 513, 583, and 6, 827, 138, the entireties of each of each of The seesaw 5 can include a spout (not shown) to allow the tube 42 to pass through the baffle 5 and allow the baffle 50 to maintain the tube 42 in an aligned and desired position. The baffle 5〇 guides the shell side fluid through the shell in a spiral flow pattern. The baffle 50 is disposed in the heat exchanger 30 such that the baffle 50 approaching the casing side inlet 46 has a different helix angle from the baffle close to the casing side outlet 48. The helix angle of the jaws can be determined, for example, by "unrolling" the helix to form a two-dimensional representation of the helix pattern. As indicated by the baffle 50a of Fig. 2, the spiral angle will then be determined by dividing the circumference of the casing C by the pitch (the extension of the cross-section by a baffle arc 360). The pitch is equal to: P = C*tan(p); where β is the helix angle. Therefore, the helix angle β is equal to arctan (p/C). As illustrated, the heat exchanger is equipped with a helical baffle 5〇 oriented vertically. The baffle 50 near the shell side inlet 46 may have a helix angle α. The baffle 50 near the shell side outlet 48 has a helix angle β with respect to the longitudinal axis A-A of the shell 44. Thus, for example, for a vaporized two-phase shell 9 201007114 side feedstream entering via the shell side inlet 46, the baffle 50 proximate the inlet 46 is configured with a small helix angle a; that is, a profile closer to the shell side outlet 48 The plate 50 is closer to the perpendicular to the axis Α-Α, having a helix angle β, wherein the heat exchange is expected to be a gas/gas of a higher shell side volume flow, such as due to evaporation, combustion, and/or fluid heating of the shell side Gas/gas. A small helix angle α thus allows the two-phase input stream to rotate in a helical path at a speed that avoids phase separation. Since the shell side fluid is a gas/gas close to the outlet 48, a helix angle β greater than the helix angle α can be used' thus resulting in a lower pressure drop than the entire length of the shell 44 using the helix angle a. In some embodiments, the baffle between the shell side fluid inlet 46 and the outlet 48 can have a helix angle γ between the helix angles α, β. For example, depending on the type of service (e.g., condensation, evaporation, etc.), the helix angle of the baffle 50 can be gradually increased or decreased from the inlet 46 to the outlet 48. In other embodiments, the helix angle of the seesaw 50 may undergo one or more changes. As described above, a heat exchanger having a _ varying spiral angle in accordance with the embodiment disclosed herein can be used when a two-phase fluid flow is anticipated. A smaller helix angle provides a higher gas phase velocity when two phase flows are expected, avoiding shell side phase separation. The helix angle of the baffle near the inlet and outlet may be the relative density of the two phases, the size of the solid and/or liquid particles or droplets (related to the velocity of the particles or droplets), the typical feed rate, and the portion The loading or reduction of the feed rate, the rise in the temperature of the shell side fluid, and other variables in the art that are conventionally known to those skilled in the art. The vertical combined feed/exit heat exchanger described herein can be used from 5. To 45. , including a 201007114 baffle with an approximate helix angle in the range of 5° to 45°. Any combination of baffle angles α, β, and γ that establish an approximate helix angle, if present, can be used in accordance with the embodiments disclosed herein. For example, in some embodiments, the helix angle a can be from about 5. It is in the range of about 45°; in other embodiments it is about 5. To 35. Within the scope; and in other embodiments at about 5. To 25. Inside. In other embodiments, the helix angle β can range from about 15° to about 45°; in other embodiments, at about 25. To 45. Within the scope; and in other embodiments, at approximately 35. To 45. Inside. A heat exchanger according to embodiments disclosed herein may advantageously be used with a shell side fluid having two or more phases. A heat exchanger according to embodiments disclosed herein advantageously provides a shell side fluid flow rate, such as by having a baffle having a small helix angle expected to be a two phase flow, to minimize or avoid fluid phase separation through the shell. In addition, the use of a larger helix angle, which is expected to be a single-phase flow, advantageously provides a lower pressure drop than when a fixed helix angle is used throughout the shell. Thus, the heat exchanger according to the disclosed embodiments can maintain a two-phase fluid flow even at a significantly reduced throughput level compared to conventional heat exchangers having a fixed helix angle, thus advantageously allowing a comparison Large throughput range. While the present disclosure includes a limited number of embodiments, those skilled in the art having the benefit of the present disclosure will understand that other embodiments that do not contradict the spirit of the disclosure may be devised. Therefore, the scope should be limited only by the scope of the attached application. [Simple description of the enclosure] Fig. 1 is a schematic view showing the fluid distribution 201007114 in a conventional shell and tube heat exchanger. 2 is a schematic diagram of a vertical combined feed/exit heat exchanger having a variable thermal baffle angle in accordance with an embodiment disclosed herein. [Main component symbol description] 30... Heat exchanger 46... Shell side fluid inlet 32... Tube side inlet manifold 48... Shell side fluid outlet 34... Fluid inlet 50, 50a···Baffle 36... Hole 38... Tube side outlet Manifold AA...longitudinal axis C...circumferential ❿ 40...fluid outlet p...pitch 42...tube 44...shell α,β,γ···Helical angle reference 12