AFTER a sporadic start in the early nineteen-fifties, books in English on the design of buildings in relation to climate appeared at a rate which reached. MANUAL OF TROPICAL HOUSING AND BUILDING For our entire .. composite climates Shelter for tropical upland climates 8 Design aids. by O H Koenigsberger, T G Ingersoll, Alan Mayhew. Designed as a textbook for students of architecture, housing, environmental design and climate control in tropical countries, this book deals with the theory of climatic design and shows how practical solutions are derived from.
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Manual of tropical housing and building: climatic by O H Koenigshberger · Manual of tropical housing and building: climatic design. by O H Koenigshberger. Manual of tropical housing and building / O.H. Koenigsberger [et al.] Koenigsberger, O. H. (Otto H.), [and others]. Part 1., Climatic design. [Harlow]: Longman. Download as PDF, TXT or read online from Scribd Climatic Design . Paix: The design of buildings for daylighting Commonwealth Exp. The first draft of the Manual served to structure their discussions and was gradually developed and changed in Yet the most pressing housing needs of the tropics are urban.
The occupants of a building judge the quality of the design from a physical as well as an emotional point of view. It is a challenge for the designer to strive towards the optimum of total comfort. Considerable information has by now been published on the physical side.
To appreciate the effect of these climatic factors. Interest in establishing thermal comfort criteria dates back in Europe about years. The following table indicates the rate of excess heat output of the body in various activities. This excess heat production varies with the overall metabolic rate. Most of the biochemical processes involved in tissuebuilding. Criteria of total comfort depend upon each of the human senses. Activity watts Sleeping min.
In the following paragraphs. Of all the energy produced in the body. Basic warmth criteria were first established in the mining. The total metabolic heat production can be divided into basal metabolism. All energy and material requirements of the body are supplied From consumption and digestion of food.
Human response to the thermal environment does not depend on air temperature alone. The physiological responses to specific climatic conditions. The processes involved in converting foodstuff into living matter and useful form of energy are known as metabolism . It has been established beyond doubt that air temperature. If there is some form of simultaneous heat gain from the environment e.
Evaporation takes place in the lungs through breathing. Radiant heat loss depends on the temperature of the body surface and the temperature of opposing surfaces. Fig 26 Body heat exchange Conduction depends on the temperature difference between the body surface and the object the body is in direct contact with.
In order to maintain body temperature at this steady level. Convection is due to heat transmission from the body to the air in contact with the skin or clothing which then rises and is replaced by cooler air.
Evaporation heat loss is governed by the rate of evaporation. Intermittent heavy lifting. The body can release heat to its environment by convection. The rate of convective heat loss is increased by a faster rate of air movement. If the vasomotor regulation is still insufficient.
These may involve the change in the basal metabolic heat production. If the heat gain and heat loss factors are: The thermal balance of the body is shown by Figure 27  and can be expressed by an equation.
The mechanism is as follows: For example. The importance of these factors should now be obvious: When both the convective and radiant elements in the heat exchange process are positive. The following paragraphs will examine how these four climatic variables affect the heat dissipation processes of the human body for various indoor conditions. As the air temperature approaches skin temperature. As long as the average temperature of opposing surfaces is below skin temperature.
Radiant heat from the sun or a hot body a radiator or fire can be a substantial heat gain factor. Moving air will remove this saturated air envelope and the evaporation process can continue.
When the air is completely saturated and warmer than the skin. Conditions which are perfectly comfortable. Fortunately such conditions are seldom met in nature. This is a circulatory failure.
Manualoftropicalhousing Koenigsberger 150824122547 Lva1 App6892
One of the basic needs of humans is change and variation. Exposed to a new set of climatic conditions. Even in warm-humid regions the highest humidities are experienced when air temperature is below skin temperature.
Even if the physiological control mechanisms can maintain life e. The body temperature would begin to rise. This point becomes particularly noticeable in mechanically controlled environments. Thermal preferences are however influenced by a number of subjective or individual factors. There will be a convective and radiation heat gain. Acclimatisation has been mentioned in 2. Such conditions rarely.
What the designer should aim at. Factors which may provide immediate relief. Clothing can be varied at the discretion of the individual. Sweating would be profuse. Subcutaneous fat. A thin person has a much greater body surface than a short. It has been demonstrated  that the lightest skin reflects about three times as much solar radiation as the darkest — the light skin.
State of health also influences thermal requirements. Dark skin also increases the heat emission from the body in the same proportion as it affects absorption. Dark skin contains appreciably more melanin pigment. The tolerable range of temperatures will be narrower.
Food and drink of certain kinds may affect the metabolic rate. Women also have slightly slower metabolic rates than men. Body shape. Age and sex may influence thermal preferences: In an illness the metabolic rate may increase. Thus skin colour has no effect on thermal preferences. A fat person will need a cooler air to dissipate the same amount of heat. Skin colour may influence radiation heat gain. During the past 50 years many attempts have been made and many experiments have been carried out in order to devise a single scale which combines the effects of these four factors.
Various research workers have devised some thirty different thermal index scales. Such scales are collectively referred to as 'thermal indices' or 'comfort scales'. In most of these experiments special rooms were built and used. A number of experimental subjects were located in the room. They named the new scale as effective temperature and it can be defined as the temperature of a still.
Fig 28 Psychrometric chart with effective temperature lines After Houghton and Yaglou: Their findings were plotted on a psychrometric chart. In Yaglou slightly revised the scale. This scale is at present the most widely used one. Shaded area: The most important ones are described in the following paragraphs. Subjective responses of acclimatised subjects were recorded together with measurements of air temperature.
Studies were carried out for a specific region with cool conditions. The method of measuring the rate of sweating was developed during experiments carried out for the British naval authorities in The cooling effect of air movements at high humidities is underestimated.
The nomogram defining it is almost identical with the ET nomogram. The sweat rate scale was established on the basis of many different combinations of the above variables producing the same sweat rate.
Herrington and Gagge. After correlating the findings. Surface temperatures of skin and clothing were also measured and recorded. It combined the effects of radiation and air temperature.
The subjects were engaged in light work. Metabolic rates as well as clothing. The calculation is based on a refined biophysical model of the man-environment thermal system. He has constructed a bioclimatic chart Figure Although his conclusions are seen to be perfectly valid.
It will be used throughout the following sections as a method for translating regional and site climatic data into a single index figure. Its usefulness extends from comfortable to overheated conditions as far as the physiological adjustments are able to maintain thermal balance. On the basis of this and similar doubts V Olgyay arrived at the idea. As a consequence of this. The index takes into account all the subjective and objective thermal factors.
Due to the rather complex calculations involved. Perhaps the only exception is the CET scale. Several physiological assumptions were made and calculation methods evolved to find an indication of heat stress on the basis of environmental measurements. The index of thermal stress developed by him is the calculated cooling rate produced by sweating. The word guide' is. Some of these difficulties arise from the fact that the experiments were carried out under widely varying indoor climatic conditions.
Metabolic heat production of subjects doing various kinds of work was measured and taken as an indication of heat stress . This is the most widely used and best understood scale — although its accuracy is doubted by some research workers  it is adequate under most conditions. Fig 29 Bioclimatic chart for men at sedentary work — wearing 1 clo. Figure 30 shows this nomogram at a scale large enough for practical work.
It has been found. These scales still do not make any allowance for radiation heat exchange between the body and its environment. This is the 'normal' scale. The same nomograms can be used for the definition of either scale. Incorporating the appropriate modifications. Values obtained in this case are referred to as corrected effective temperature or CET.
Subsequent findings [36 and 39] have proved that this method underestimates the significance of moderate air movements at high temperatures and at the same time overestimates the adverse effect of higher humidities.
For persons stripped to the waist. Both nomograms are reconstructed on the basis of those published in Bedford's work. Strictly speaking. It has an inertia of some 15 minutes. For the purposes of the CET nomogram the globe thermometer readings can be used without any correction.
If the air is warm. Mean radiant temperature is defined as follows: It can be measured directly with the globe thermometer Figure 32 which consists of an ordinary mercury thermometer enclosed in a matt black painted copper globe of mm diameter.
For conditions other than this. If radiation is received the reading will be higher than the air temperature. Fig 31 Basic effective temperature nomogram for persons stripped to the waist 2. The Kata thermometer is an instrument used for this purpose. The spirit is heated to expand to the small container at the top. There are two markings on the tube. If the air is still 0. The nomogram given on Figure 33 is now used as follows: The time it takes for the spirit to drop from the upper to the lower marking is measured by a stop-watch.
It is a glass tube. When taken out of the water. Fig 32 The globe thermometer Anemometers with moving mechanical parts will rarely respond to air movements below 0. The specific properties of each thermometer are expressed by a number. On the basis of Singapore and Australian data it seems to be justified to adopt the values given in the last line of the table as valid for most tropical climates. This has been shown on the bioclimatic chart Figure Fig 33 Kata air speed nomogram 2. The following table compares the findings of several research workers and shows that there is considerable discrepancy between the various limits arrived at.
Below 0. It is a composite climate with three distinct seasons. With an air velocity of 0. The comfort zone must also be limited in terms of air velocities. Figure 35 shows the nomogram. It can be seen that with little or no air movement this condition is uncomfortable.
This is not a rigid limit: This indicates that with air movements between 0. If the globe thermometer temperature is not available but the DBT is known. Above 1. Thus the shaded quadrangle in Figure A more detailed analysis of the climate of Islamabad is shown in Figure 36 as an example. This can be done for the mean maximum and mean minimum values for each month and shown graphically.
This data is converted into CET values and plotted on a diagram to show the diurnal changes on these three days. The average value is taken as 1. If there is a strong radiation source. If the wet-bulb reading is not available. Distinctions are also made between spaces exposed to or protected from the wind.
For the purpose of constructing such a chart. From these define the maximum ET using nomogram of Figure 30 — then locate this on the top scale 2 take the mean minimum temperature and the morning humidity. Figure Wind could bring some relief. Such data is rarely available. Several assumptions can however be made to simplify this task: Fig 34 Effective temperature histogram Baroda Studies such as this assist the designer to define the control functions expected of the building and establish criteria for the design of the building fabric.
The diagram reveals that there is considerable 'underheating' in the cold season and practically constant 'overheating' in the hot-dry season. Fig 35 An example of using corrected effective temperature. Results are transferred to the isopleth chart. Mean maximum and mean minimum DBT values. Maximum and minimum ET values are found from Figure Figure 37 is used to interpolate 2-hourly values.
Further use of this will be shown in 4. WBT values are obtained from Figure Fig 38 Effective temperature isopleth and its computation New Delhi. This is taken as a unit of clothing.
Manual Tropical Housing Building Climatic Design
India 1. The maximum practicable. Section 3 Principles of thermal design 3. If energy is conveyed to a body. A position on this scale. Only in possession of this knowledge and with a clear understanding of the principles involved can the designer avoid some of the popular misconceptions.
Temperature is measured by the Celsius scale. Both should be pronounced as 'degrees Celsius'. If the methods of control were to be learned in applied form only. For a more detailed treatment of physical principles refer to the works listed under item [40—42] of the bibliography.
The popularly used name centigrade' should be avoided. If this molecular movement is spreading to other bodies e. This has been constructed by taking the freezing and boiling points of water at normal atmospheric pressure as fixed points and dividing the interval into degrees. It would be advisable to completely delete the term 'weight' from the vocabulary and speak either of mass or of force as it blurs the fact that mass units kg or lb are not the same as force units kgf or lbf.
The British Thermal Unit Btu was defined as the amount of heat necessary to raise the temperature of 1 lb of water by 1 degF. J Previously special units were is use for the measurement of heat.
Manualoftropicalhousing Koenigsberger 150824122547 Lva1 App6892
Both of these are now obsolete. As such. Heat is a form of energy. Weight is actually the gravitational acceleration of a unit mass. The kilocalorie kcal was defined as the amount of heat necessary to raise the temperature of 1 kg of water by 1 degC.
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This unit is given the special name 'Newton': N Note that as the gravitational acceleration is 9. Old data can be converted into SI units by using the following factors: Specific heat of a substance is the amount of heat energy necessary to cause unit temperature increase of a unit mass of the substance.
It is measured in: The higher the specific heat of a substance, the more heat it will absorb for a given increase in temperature. Of all common substances water has the highest specific heat: Latent heat of a substance is the amount of heat energy absorbed by unit mass of the substance at change of state from solid to liquid or liquid to gaseous without any change in temperature.
At change of state in the reverse direction the same amount of heat is released. Thermal capacity of a body is the product of its mass and the specific heat of its material. It tends to flow from high temperature to lower temperature zones, by any or all of the following ways: The greater the temperature difference, the faster the rate of heat flow. An outline of the physical principles and of the quantities involved is given in the following paragraphs, and methods of calculating the heat flow rate will be described in section 3 2.
W If unit work is carried out in unit time, or unit energy is expended to unit time, we have unit power. Thus if we think of power as the rate of energy expenditure, it will be seen that the same unit can be used to measure the rate of energy flow. This energy flow may be the flow of heat. In all these cases energy is flowing or expended, and it is the rate of this flow which we measure in watts. The following conversion factors can be used to convert old data into watts: The common element in all these units is that all are energy units per a time unit, which may be a second, an hour or a day, as in the last item.
A ton of refrigeration is the cooling power of 1 ton American 'short' ton of lb of ice melting in 24 hours. As a pound of ice requires Btu of heat to melt it into water of the same temperature: In many cases, however, there is no defined area through which the heat flow could be considered, e. In such cases the heat flow rate can be measured in relation to a unit area, i. The unit of measurement is watt per metre square: The rate at which such molecular movement spreads varies with different materials and is described as a property of the material — its thermal conductivity or 'k-value'.
It is measured as the rate of heat flow flow of energy per unit time through unit. The lower the conductivity, the better insulator a material is. For conductivity and resistivity values of various materials see appendix 5. The apparent relationship is due to the fact that air has a very low conductivity value, and as lightweight materials tend to be porous, thus containing more air, their conductivity tends to be less. There are, however, many exceptions, for example:.
In all three pairs the second one is lighter, but has a higher conductivity value. The relationship is true for materials of the same kind, but of varying densities, or for the same material with different densities, due to variations in moisture content. Water has a conductivity of 0. Therefore if air in the pores of a material is replaced by water, its conductivity rapidly increases.
Tests on an asbestos insulating slab gave the following values :. The more porous a material, the greater the increase in conductivity with increased moisture content.
Conductance is the heat flow rate through a unit area of the body i. The unit of. The conductance of such a multilayer body Cb can be found by finding its total resistance Rb and taking its reciprocal:. A measure of this is the surface or film-resistance, denoted thus: Surface conductance includes the convective and the radiant components of the heat exchange at surfaces.
In the preceding paragraphs, heat flow from one surface of the body to the other surface was considered thus the temperature difference was taken between the two surfaces. Conductance has been defined in these terms. If the heat flow from air on one side, through the body, to air on the other side is considered, both surface resistances must be taken into account. The overall, air-to-air resistance R is the sum of the body's resistance and the surface resistances: The magnitude of surface- or film-conductance f is a function of surface qualities and of the velocity of air passing the surface.
Values valid for moderate climates, winter conditions, are given in appendix 5. This is the quantity most often used in building heat loss and heat gain problems, as its use greatly simplifies the calculations.
Values for everyday constructions are given in appendix 5.
See also 3. It is measured as the cavity resistance, Rc which can be added to the other resistances described above. At most the value of Rc for an empty cavity may be the sum of an internal and an external surface resistances 0.
Its value can be improved significantly by hanging an aluminium foil freely, inside the cayity. The function of this will be explained when radiation effects are discussed.
Values of cavity resistances and the reciprocals, the cavity conductances are given in appendix 5. This movement may be self-generating, i.
The rate of heat transfer in convection depends on three factors: The convective heat flow from a body, through a medium, to another body is expressed by a more complex equation, not necessary for our purposes. Radiation received by a surface can be partly absorbed and partly reflected: The sum of these two coefficients is always one: For the perfect reflective theoretical white surface: The perfect absorber, the theoretical 'black body', would have the coefficients: For values of some building surfaces see appendix 5.
Its value is the same as for absorbance: The wavelength of emitted radiation depends on the temperature of the emitter. Thus the absorbance for solar radiation will not be the same as emittance at terrestrial temperatures; for example:.
The practical significance of this is that if both surfaces are exposed to solar radiation, both will reflect and absorb the same amount of heat, but the white painted surface will re-emit much of the absorbed heat, whereas the bright metal surface will not.
Therefore the latter will attain a much higher temperature. Bright metal foils are successfully used for insulation in situations where heat is transmitted mainly by radiation. A loose foil in a cavity will reflect much of the incident radiant heat, but if it absorbs any, very little of it will be reradiated. With many sources producing a complex pattern by inter-reflection, a description of the situation in these terms would be very lengthy and cumbersome. Such a situation can be described in terms of the mean radiant temperature MRT or globe thermometer readings see 2.
This can be done by using the sol-air temperature concept. A temperature value is found, which would create the same thermal effect as the incident radiation in question, and this value is added to the air temperature:. As this value can be related to the increase in the inner surface temperature. The reason is that the incident radiation increases the surface temperature far above the air temperature.
It is reasonable to assume a constant value for external surface conductance as: Good insulation with a highly reflective surface is of course. Its value should not exceed 0. From the above sol-air temperature equation the temperature equivalent of the radiation gain the sol-air excess' is: Thus the extra heat flow rate q per unit area caused by the radiation is: From this the 'solar gain factor' is: This solar gain factor is defined as the heat flow rate through the construction due to solar radiation expressed as a fraction of the incident solar radiation.
For the reduction of solar heat gain a dark. The greater the fo value. The building can similarly be considered as a defined unit and its heat exchange processes with the out-door environment can be examined see Figure The heat flow rate of such mechanical controls may be denoted as Qm. It may be denoted as Qs c Heat exchange in either direction may take place with the movement of air. This may be denoted as Qi e There may be a deliberate introduction or removal of heat heating or cooling.
Fig 39 Heat exchange of buildings a Conduction of heat may occur through the walls either inwards or outwards. These factors will be examined in the following paragraphs.
The solar heat flow equation can therefore be established as: If heat loss from a building is considered: The rate of ventilation heat flow is described by the equation: This may be unintentional air infiltration or may be deliberate ventilation. This would be the heat flow rate through an unglazed aperture.
Heat output from a body inside the building is a heat gain for the building. Thus the heat output rate appropriate to the activity to be accommodated must be selected and multiplied by the number of occupants. It can be measured indirectly.
It can thus be taken as a dependent variable in the equation. The result. The heat flow rate of these systems is subject to the designer's intentions and it is deliberately controllable. Consequently the total wattage of all lamps in the building if and when in use must be added to the Qi If an electric motor and the machine driven by it are both located and operating in the same space.
Usually evaporation heat loss is either ignored for the purposes of calculations except in mechanical installations. The estimation of evaporation rate is a more difficult task and it can rarely be done with any degree of accuracy except under mechanically controlled conditions. The total rate of energy emission of electric lamps can be taken as internal heat gain.
If the motor only is in the space considered and its efficiency is e. Thus the ventilation rate is: Under less severe conditions the installation can work with a reduced output. The calculation method is best illustrated by a simple example: It is obvious that this installation should cope with the warmest conditions at its peak capacity. The above example will be used.
If heat is to be removed at this rate by circulating cooled air. What will have to be the rate of air exchange? The supplied air. Thus from the equation: To avoid draughts. Here again. Set up a temperature scale vertically. Alongside this. Establish the To and Ti points at the faces of the resistance section.
This can be established quite simply by a graphic method. Its prediction and avoidance is an important concern of building designers in cold climates. By using the psychrometric chart Figure 12 the dewpoint temperature for air with any defined moisture content or RH can be found.
On cold walls such surface condensation may be soaked up into the wall material. This is a familiar occurrance on a bathroom mirror or on the inside of a cold window pane. This is the dewpoint temperature for the particular air. A line connecting the points thus derived will represent the thermal gradient through the wall.
The intersection points of this line with the various layers can now be projected across horizontally to the corresponding layers of the physical section. The temperature at which this happens is referred to as 'dewpoint temperature'. The prediction technique [41 and 42] is based on establishing the dewpoint temperature of the air and finding where this will intersect with the thermal gradient of the wall.
These may become involved. If this air comes into contact with a surface having a temperature less than Fig 40 Temperature gradient through a composite wall not to scale 3. Most building materials are porous and offer little resistance to the passage of vapours. If the inside humid air penetrates the wall. This phenomenon is known as interstitial condensation. He has to make decisions to determine the size.
The building designer is faced with a much more indeterminate situation. Qm — that is. The means of controlling the various factors will be discussed in Section 4. There is and there can be no set procedure for the decision sequence. As perfectly static conditions do not occur in nature. Prediction of the thermal behaviour of the building is not the aim of the exercise — the mechanical controls will provide the necessary adjustments — the designer only has to make sure that enough capacity is provided in heating or cooling to cope with the reasonably likely worst conditions.
Such a situation may prevail in the winter of moderate climates when the interior is heated and kept at a given temperature or in a warm-humid climate where the indoor temperature is kept constant by air conditioning. Calculations based on steady state assumptions are useful to determine the maximum rate of heat loss or heat gain. The steady state calculation methods can also be considered as preliminary studies. The latter is the ratio of the maximum outer and inner surface temperature amplitudes taken from the daily mean.
Thus the corresponding increase of the internal surface temperature will be delayed. From this moment the heat stored in the wall will be dissipated partly to the outside and only partly to the inside. Fig 41 Time-lag and decrement factor The out-door temperature will have reached its peak and started decreasing.
Each particle in the wall will absorb a certain amount of heat for every degree of rise in temperature. The diagram given in Figure 41 shows the diurnal variations of external and internal temperatures in a periodically changing thermal regime. The rate at which it will transmit heat to the next particle depends on two factors: Diurnal variations produce an approximately repetitive hour cycle of increasing and decreasing temperatures. In the morning. In nature the variation of climatic conditions produces a non-steady state.
Heat to the next particle will only be transmitted after the temperature of the first particle has increased. The two quantities characterising this periodic change are the time-lag or phase shift. The effect of this on a building is that in the hot period heat flows from the environment into the building. As the cycle is repetitive. As the out-door air cools. Fig 42 Decrement factor and time-lag as a function of conductance and capacity It can be visualised as the surface area of a sphere over which the temperature spreads in unit time.
To find the momentary rate of heat flow. These can be calculated for a particular construction . Fig 43 Decrement factor and time-lag values for massive walls 3. If the indoor temperature is assumed to be constant a reasonable assumption in controlled environments. A rule of thumb for massive masonry. The transmittance. The process could be described as 'balancing in time'. The thermal capacity is a factor to be considered also in moderate climates.
With a mm concrete slab. He aims at permitting heat gain through the enclosing elements when there are heat losses by other channels e. Low thermal capacity or 'quick response' structures warm up quickly but also cool rapidly.
Large thermal capacity structures will have a longer 'heat-up time' but will conserve heat after switching off the heating. Section 4. The reason for this is obvious if the mechanism of the process is observed e. Thus the selection of a construction with an appropriate time-lag is an essential factor in the design. Both lower and upper openings should be on the same side and should be closed during the day. Air flow in the cavity at night would be upwards and during the day downwards.
To remove it. As it has been shown that the insulation should be outside of the main mass. If no provision is made for closing the ventilators.
G K Kuba  suggests that the outer leaf should be constructed of hollow blocks or bricks. If this insulation is on the outside. He has also tested the effect of ventilating the cavities and arrived at the conclusion that ventilation during the day is undesirable. Applied insulation will restrict not only the entry.
The outer leaf should be of a lightweight construction. Section 4 Means of thermal control 4. As D H K Lee expressed it  'the degree of sophistication in environmental controls is largely a socio-economic question' In other words.
Precisely controlled indoor climate can only be achieved by mechanical active. Fig 44 Potential of climatic controls Structural passive means of control can provide a further levelling out of the climatic variations. Figure 44 shows that the extremities of climatic variations can be attenuated by such means. When the conditions are such that only the degree of comfort is in question — when the risk is a slight discomfort — the use of mechanical controls is optional.
The environment immediately outside and between buildings can be influenced by the design of a settlement and by the grouping of buildings to a minor extent see 1. A value judgment will be involved in deciding what degree of comfort we want to achieve and how much we are prepared to pay for it.
At most. Increased insulation would reduce the heat loss rate. Even here the heat deficit is so small that in a suitably designed and built building.
Distribution of heat. To optimise the insulation versus heating expenditure. The gas and electric heaters can be considered as using a processed fuel: Any central heating system consists of three distinct elements: Tropical upland climates are probably the only climates where cool discomfort conditions may prevail for such a length of time that the thermal storage capacity of the structure is insufficient to ensure indoor comfort.
Dryness very low humidity is a result of heating. All the various fireplaces. The temperature gradient between areas of concentrated heat loss e. This conveying medium is most often water or air. The level of centralisation can vary. Central heating is the term used to describe an installation where heat is produced at a central point the boiler or furnace.
When cool air of medium humidity is heated. Its RH increases. A supply of fresh air at a rate substantially higher than the volume of actually inhaled air will be necessary.
In many situations an adequate air supply can be ensured simply by keeping the windows and doors open. The most dependable. Condensation can be caused indirectly.
Body smells. Often a certain degree of control can be achieved by the occupants opening and closing the windows at will. The installation can take the following forms: The warm indoor air will readily take on moisture from any available source: None of these problems is likely to arise in tropical climates except with artificial cooling.
Interstitial condensation may soak the wall material and increase its conductivity. In a closed environment oxygen content is reduced and the carbon dioxide content is increased by man's presence. Biologically the limit of existence is 0. An average person. As an example. A fan giving the above ventilation rate can be selected from catalogues. With a plenum or balanced system the air will normally be filtered at the point of intake.
Another form of cooling by air movement is the 'physiological cooling' 2. It can. Ventilation can also provide a cooling effect simply by replacing the warm inside air with cooler outside air. The above is an approximate calculation only: Warm air heating is usually combined with a mechanical ventilation system. This is achieved by table-top or ceilingmounted fans punkahs. In cold climates the need for cooling rarely arises.
Using the ventilation heat loss equation 3. These can be cleaned and reused c washing. In warm climates the intention is to keep the indoor air cooler than the out-door air. The warm coil is thus kept under high pressure and the cold coil under a negative pressure.
It may serve three purposes: In a mechanical installation. Without changing the heat content. In large plants. It has been mentioned 3. The refrigerant is in a liquid state under compression and in a gaseous state under low pressure. This is most often a gas called Freon CF2Cl2.
A suitable gas. This is likely to be the case in hot-dry climates. The two coils are connected on one side through a compressor and on the other side through a pressure release valve. Such water sprays can be utilised in warm-humid climates only as a preliminary treatment of air if it is to be subsequently dehumidified.
This phenomenon can be successfully utilised for the cooling of air when the air itself is dry. It must be followed by a set of 'eliminator plates' which would trap and drain away any small droplets of water carried by the fast moving air stream. The circuit consists of two coils: Fig 45 A Refrigeration heat-pump circuit the warm coil or condenser.
The latent heat of evaporation. When liquefying. Fig 46 Air cooler arrangement 4. The cycle can be described as follows: Its meaning and derivation has been explained in 3. The method is best illustrated by an example. When air is cooled to its dewpoint.
The question now is: When it reaches the extreme curve. The values in bold type are the ones found from the psychrometric chart: Incidentally it can be established that the 13 — 7. AH and WBT are known. In the refrigeration plant the 23 kW electric motor is working to cause the removal of heat at the rate of 50 kW.
The only way to remove moisture from the air is to force it to condense out. This condensate may be drained away. As the AH at This can only be done by cooling. Thus cooling must be combined with some form of mechanical ventilation system. What must be done here.
If doors and windows are closed. The downwards movement indicates that moisture is being condensed out. All this can be done by using the psychrometric chart without any calculations. It will actually reach saturation point at As an actual piece of machinery. Fig 47 An air conditioner In principle a building installation can take one of the following three forms: Figure 47 shows the schematic arrangement of an air conditioner. It is distributed through small size circular ducts usually at high velocity and before being discharged it is mixed with the.
Without dehumidification the system is not air conditioning. In an extreme case it can happen that the northern part of a building requires heating. For such extremes. In its more refined form the air conditioning installation becomes a self-regulating homeostatic system. Heat losses may depend on the direction of wind. Variations of solar heat gain differ from elevation to elevation.
Such a control system has three major types of components: Internal heat gains may vary from one part of the building to another. The environmental elements aiding us have their limits.
These statements express an unequivocal ethical attitude to architectural design. But it is expected that the architect should build the shelter in such a way as to. V Olgyay arrives at a similar conclusion by way of a pragmatic approach: Where the direction of heat flow is twice reversed in every hour cycle.
The theory of periodic heat flow and the concepts of time-lag and decrement factor have been introduced in Section 3. Search WorldCat Find items in libraries near you. Advanced Search Find a Library. Showing all editions for 'Manual of tropical housing and building' Sort by: Refine Your Search Year. Select All Clear All Save to: Your list has reached the maximum number of items. Please create a new list with a new name; move some items to a new or existing list; or delete some items.
Remember me on this computer. Cancel Forgot your password?The outer leaf should be of a lightweight construction. It can be seen that with little or no air movement this condition is uncomfortable. The present work concerns itself with tropical climatic zones only.
It is not a matter of the total amount of land available. Moving air will remove this saturated air envelope and the evaporation process can continue. Hail may also occur.
Diffuse radiation is only present during dust haze periods. When the air is completely saturated and warmer than the skin. If not, and if the given site is in or near a major seismic zone, expert advice should be sought, either regarding the least risky part of a large site or just to establish the degree of risk, so that appropriate precautionary measures can be taken.
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