An example of countercurrent heat exchange occurs in the feet of penguins, in which heat from blood in the arteries supplying the feet is transferred to blood returning to the bodys core in veins that lie. Source for information on countercurrent heat exchange. Countercurrent heat exchange and thermoregulation during. The mechanisms shown here are traditionally called the countercurrent multiplier and the countercurrent exchanger. The most dramatic example is found in the swim bladder of deep sea fish to regulate their buoyancy at depths of thousands of meters fig. Arteries to the skin carrying warm blood are intertwined with veins from the skin carrying cold blood, causing the warm arterial blood to exchange heat with the cold venous blood. There are different forms of socalled crossflow heat exchangers in which the flows are more or less mutually perpendicular. Botz3 1department of ecology and evolutionary biology, university of california, irvine, california. They are most commonly found in the circulatory, respiratory, and excretory kidney systems, serving in heat, oxygen, and ion exchange. Heat exchanger heat exchange is an important unit operation that contributes to efficiency and safety of many processes. The mechanisms effect is dependent on the two fluids flowing in opposite directions, and having a concentration gradient between them.
Besides conservation of heat, countercurrent exchange has a wide variety of applications in biology table 1. Countercurrent exchanger definition of countercurrent. Previous topic previous slide next slide next topic. Some animals use body insulation and evaporative mechanisms, such as sweating and panting, in body temperature regulation. Countercurrent heat exchange with vaporizing immiscible. Pdf heat exchanger lab experiment chemical engineering. Countercurrent exchange is a key concept in chemical engineering. Unit operations lab heat exchanger 11 heat exchanger heat exchange is an important unit operation that contributes to efficiency and safety of many processes.
Jackson, knut schmidtnielsen proceedings of the national academy of sciences jun 1964, 51 6 11921197. However, the term is commonly used to equipment in which two process streams exchange heat with each other. Countercurrent exchange is a mechanism occurring in nature and mimicked in industry and engineering, in which there is a crossover of some property, usually heat or some chemical, between two flowing bodies flowing in opposite directions to each other. Charts of f for the common shell and tube exchanger configuration are discussed later.
Pdf a laboratory exercise using a physical model for. Learn countercurrent heat exchange with free interactive flashcards. Heat exchangers in marine mammals, an example of countercurrent. This is a significant way to save heat, as the heat would otherwise be lost to the water the whale swallows.
When you consider that the blood of fishes passes over the gills which are bathed in the surrounding water, it is easy to see why fishes are coldblooded. The first takes place in the region of the nephron called henles loop. Countercurrent exchange in the renal medulla american. For an existing heat exchanger the geometry, flows and. Experiment regarding heat exchanger concurrent countercurrent flows at same rate and different rates. Parallel and counter flow designs heat exchangers although ordinary heat exchangers may be extremely different in design and construction and may be of the single or twophase type, their modes of operation and effectiveness are largely determined. Countercurrent exchange biology accessscience from mcgraw. However, the vein returning blood to the body core lies alongside the artery taking blood to the feet. A sea gull can maintain a normal temperature in its torso while standing with its unprotected feet in freezing water. Heat exchangers are used in both cooling and heating processes.
Modeling countercurrent arteriovenous heat exchange and blood. Countercurrent heat exchange and thermoregulation during blood. An example of countercurrent heat exchange occurs in the feet of penguins, in which heat from blood in the arteries supplying the feet is transferred to blood returning to the bodys core in veins that lie close to these arteries. Pdf a heat exchanger is a device in which energy is transferred from one fluid to another across a solid surface. Pdf file of the complete article 629k, or click on a page image below to browse page by page.
A theoretical model is developed to describe the effects of blood flow rate and vascular geometry on the thermal equilibration in the carotid artery based on the blood. The nondimensional parameters that govern the mechanism have been determined in terms of the properties of the animal. Here, we will cite only those that are immediately useful for design in shell and tube heat exchangers with sensible heat transfer on the shellside. Countercurrent exchange biology accessscience from. This study focusses on the thermal stimulation using a countercurrent heat exchange reactor for the in situ combustion of. The velocit oyf blood flow in the exchange irs about i8ot ohf that in the dorsal aort anad postcardinal vein allowing time for heat transfer. The flows inside a heat exchanger can be arranged in various ways to fulfil different purposes. Countercurrent heat exchange in vertebrate limbs the. The model demonstrated the advantages of countercurrent exchange as a critical trait in mediating convective heat loss in an organism, thereby. Wilhelm kriz, brigitte kaissling, in seldin and giebischs the kidney fifth edition, 20.
As warm blood flows to the tongue through an artery, it gives off heat to the blood returning to the whale through its veins. A countercurrent heatexchange reactor for the thermal. The kissing bug heat exchanger could also serve as inspiration for equivalent technological systems. Countercurrent exchange circuits or loops are found extensively in nature, specifically in biologic systems. This is referred to as the countercurrent exchange mechanism. As blood flows to the tip of the tongue, it heats up blood returning to the body. The term heat exchanger applies to all equipment used to transfer heat between two streams. Choose from 359 different sets of countercurrent heat exchange flashcards on quizlet. The flowing bodies can be liquids, gases, or even solid powders, or any combination of those. Nov 21, 2017 thank you for submitting your article countercurrent heat exchange and thermoregulation during bloodfeeding in kissing bugs for consideration by elife.
Countercurrent heat exchange with vaporizing immiscible transfer agent. Thermoregulation temperature regulation strategies. Mar 16, 2019 a special circulatory adaptation known as countercurrent heat exchange enables both of these animals to maintain the appropriate body temperature in their extremities, and this is only one of the many clever adaptations mammals have evolved over the last hundred million years to help them to deal with variable temperatures. Such countercurrent systems have been utilized numerous times by living organisms for all types of exchange function. The basic design equation and overall heat transfer coefficient the basic heat exchanger equations applicable to shell and tube exchangers were developed in chapter 1. Last but not least, kissing bugs spread the parasites that. A countercurrent heat exchanger is an arrangement of blood vessels in which heat flows from warmer to cooler blood, usually reducing heat loss. Parallel and counter flow designs heat exchangers although ordinary heat exchangers may be extremely different in design and construction and may be of the single or twophase type, their modes of operation and effectiveness are largely determined by the direction of the fluid flow within the exchanger.
For an existing heat exchanger the geometry, flows and specific heats of the flows give the effectiveness. The vessels in the tuna heat exchanger are an order of magnitude larger. Countercurrent exchange is a mechanism widely used by different species for a variety of purposes. A number of minicolumns are set up in series, and the pregnant solution is passed through the columns, countercurrently to. A laboratory exercise using a physical model for demonstrating countercurrent heat exchange article pdf available in ajp advances in physiology education 361. Countercurrent exchange of heat, respiratory gases, or nutrients is an important feature of the functional design of organisms, is covered in most undergraduate physiology textbooks e. Countercurrent heat exchange in the respiratory passages. Doc report heat exchanger ridzuwan rahimi academia. Teaching in the laboratory a laboratory exercise using a physical model for demonstrating countercurrent heat exchange catherine loudon,1 elizabeth c. A special circulatory adaptation known as countercurrent heat exchange enables both of these animals to maintain the appropriate body temperature in their extremities, and this is only one of the many clever adaptations mammals have evolved over the last hundred million years to help them to deal with variable temperatures. Counter current exchange is the mechanism by which some property of a fluid, such as heat or a chemical substance, is transferred from one fluid across a semipermeable membrane or thermally conductive material to another fluid flowing in the opposite direction. Figure 1 counter current heat exchanger made or arteries and veins in the fins of a dolphin. The relative decline in expired air temperature te, andhence the quantity of water recovered, is a function of the geometry and temperature of the surfaces available for heat exchange.
An analytical model of the countercurrent heat exchange. To be able to perform the measurement, recalling the things studied in that subject is necessary. Thank you for submitting your article countercurrent heat exchange and thermoregulation during bloodfeeding in kissing bugs for consideration by elife. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. Countercurrent exchange in a utype countercurrent exchanger may have two functions.
Countercurrent heat exchangers occur naturally in the circulation system of fish, whales and other marine mammals. Theoretical evaluation of contributions of heat conduction. View enhanced pdf access article on wiley online library html view download pdf for offline viewing. Engineering a model for countercurrent heat exchange. Chapter 5 heat exchangers faculty of engineering and. This results in absorption of water into the blood and return of the absorbed solute to the interstitium. The possibilities are countercurrent flow, cocurrent flow and crossflow, the first two of which are shown in figure 1.
The overall heat transfer coefficient of the exchanger is. In general, countercurrent exchange is a crossover of a certain property, f. Theoretical summary the basic operating principles and the simplified calculations regarding the counter current heat exchanger were discussed in the subject chemical unit operations i. Through natural selection, a countercurrent heat exchange system was established in the gray whales tongue. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural. Therefore, for modeling heat transfer in these tissue regions, reasonable assumptions related to the countercurrent heat exchange mechanism can be made to simplify the mathematical formulation.
In animals where water recovery via temporal nasal countercurrent exchange is high, this area is large collins et al. Under warm environmental conditions, the venous flow is shunted to superficial veins to facilitate heat transfer from the fin. All these heat exchangers can be operated in both parallel and. Yet, blood is not freely available in nature, but it circulates inside. Sep 16, 2016 countercurrent exchange is a mechanism widely used by different species for a variety of purposes. Bloodsucking insects experience thermal stress at each feeding event on endothermic vertebrates. The basic operating principles and the simplified calculations regarding the counter current heat. In vertebrates, they are called a rete mirabile, originally the name of an organ in fish gills for absorbing oxygen from the water. Ther aree many valves in the segmental veins which ma bye expected because of the resistance offere byd the exchanger. A detailed analysis of this type of heat exchanger is therefore necessary. Countercurrent flow between blood and seawater in fish gills maximizes extraction of oxygen. Pdf countercurrent heat exchange and thermoregulation during. Countercurrent vascular heat exchange in the fins of whales. In a counterflow or countercurrent heat exchanger, hot and cold fluids enter the exchanger from opposite sides.
Countercurrent heat exchange flashcards and study sets quizlet. In the nose, a single passageway facilitates inhalation of dry, cool air and exhalation of warm, moist air. For a more enjoyable learning experience, we recommend that you study the mobilefriendly republished version of this course. In this case, the separation of the two fluids inhaled and exhaled. Countercurrent ion exchange ccix tests kotze et al.
Countercurrent heat exchange in desert animals spatial. Countercurrent heat exchangers can operate with remarkable efficiency. Thermoregulation temperature regulation strategies article. Heat moves by conduction from the warmer arterial blood to the cooler venous blood. The first page of the pdf of this article appears above. An analytical model for the countercurrent heat exchange mechanism in animals has been formulated and a solution has been obtained. The purpose of this work is to evaluate the capacity of the heat loss from the carotid artery in the human neck and thus, to provide indirect evidence of the existence of selective brain cooling in humans during hyperthermia. A heat exchanger is a system used to transfer heat between two or more fluids. Countercurrent heat exchange is a common mechanism in organisms that utilizes parallel pipes of flowing fluid in opposite directions in order to save energy. Parallel and counter flow designs heat exchangers engineers. All these heat exchangers can be operated in both parallel.