Eksperimentalnoe research of heating of interglass space at threefold osteklenii

For maintenance of comfortable conditions indoors it is necessary, that difference of temperatures between air temperature indoors and temperature of internal surfaces of protecting designs was minimum. The lowest during the winter period of time indoors usually is the surface temperature ostekleniya windows that creates discomfortable zones near to them. Therefore actual the problem of working out and research of new designs of windows with more heats of an internal surface ostekleniya is represented.

In connection with icrease of requests to resistance to a heat transfer svetoprozrachnyih protecting designs in the conditions of a city of Tomsk for residential buildings the resulted resistance to a heat transfer for windows and balcony doors should be not less than 0,64 m І • ° With/vt. At the same time resistance to a heat transfer for threefold ostekleniya in wooden or plastic covers makes 0,55 m І • ° With/vt. Thus, for fulfilment of existing standard requests for conditions of a city of Tomsk it is necessary to pass to other kinds of window fillings, that, as a rule, reduces svetopropuskanie, complicates a design of a window and increases its cost.

One of effective methods of rise in temperature internal ostekleniya is electric heating of windows. Variants of use electrowarmed ostekleniya which is especially effective together with application teplootrazhayuschih covers are known. There are data of tests of electric heating of an interglass air interval at double osteklenii. In the given work results of an experimental research of influence of a thermal emission in interglass space on temperatures of surfaces ostekleniya and resistance to a window heat transfer are presented at threefold osteklenii.

Experiments are conducted in the climatic chamber. The tested fragment ostekleniya represented a single-chamber double-glazed window (a thickness of an air layer — 16 mm, a thickness of glasses — 4 mm) and unary osteklenie in the thickness of 6 mm established in the general frame. The distance between a double-glazed window and unary ostekleniem made 57 mm. The sizes ostekleniya were 325h825 mm І. In the centre of an air interval between a double-glazed window and unary ostekleniem on all width of a window in the bottom part at height of 20 mm from a bottom edge ostekleniya have been established a cylindrical ohmic heater. In experiences the thermal stream made through a heater per unit of length of a bottom edge ostekleniya, was changed from 27 to 100 Vt/m. Temperature in cold branch of the climatic chamber during realisation of experiments was-35°S, in warm branch +18°S.

The field of local thermal streams on a glass surface was measured by gauges of thermal streams, temperatures of glasses in various points of a surface were defined by the microthermocouples established on an internal and outside surface of a window.

In the basic series of experiments the double-glazed window has been established from cold branch of the climatic chamber. Distributions of temperatures and density of thermal streams for various capacities of thermal emissions in a thermal air layer are received. As a result of realisation of experiments it has been established, that the above load on a heater, the the temperature ostekleniya is more considerably lifted. More essential rise in temperature on a surface ostekleniya was observed from a premise, is closer to which the heater (fig. 1,) is established. Smaller influence heating on temperature external ostekleniya (rendered fig. 1,).

Thus, during experiments it has been established, that at small thermal emissions of 50-100 Vt/m in the bottom part of an air layer at three-layer osteklenii, it is possible to achieve essential rise in temperature of internal glass in the bottom zone and to create more uniform distribution of temperatures on height ostekleniya from a premise.

Measurements of thermal streams from the warm and cold parties of a window are conducted at different capacities of heating. From the executed measurements the thermal stream leaving through osteklenie from a premise follows, that with increase in capacity of thermal emissions, decreases, that is connected with decrease in difference of temperatures between temperature ostekleniya and air temperature indoors.

With increase in the capacity submitted on a heater, resistance to a heat transfer of a design "double-glazed window-glass" which was defined by standard image has increased: the relation of a difference of temperatures between temperatures of internal and outside air to the density of a thermal stream going from a premise through osteklenie. So, without heating resistance to a heat transfer of the given design for standard conditions (at factors of a heat transfer from internal and outside surfaces of 8,2 and 23 Vt/m І • ° With accordingly) made 0,56 m І • ° With/vt, at load on a heater of 27 Vt/m — 0,77 m І • ° With/vt, and at 50 Vt/m — 1,02 m І • ° With/vt.

Change of temperature in the bottom zone ostekleniya, at different capacities of load of a heater, with the course of time from the beginning of work of a heater is shown on fig. 2. For temperature of the bottom zone ostekleniya the temperature which the thermocouple established on osteklenii above its bottom edge on 100 mm showed started. From drawing follows, that the the big capacity we submit on a heater, the it is required to more time for a temperature exit ostekleniya on an equilibrium condition. At a mode of heating time of an exit for a stationary mode made of 50 Vt/m the little more than 60 mines, and level achievement in 90 % from equilibrium temperature occurred within the first 30 minutes

On fig. 3 approximating dependence of results of the conducted experiments, showing is resulted, what maximum rise in temperature on an internal surface of glass occurs owing to giving of this or that electric capacity on a heating element. On this drawing it is possible to determine the size capacities which is necessary for submitting on a heater for maintenance of the required temperature on a surface ostekleniya in the bottom zone and, on the contrary, knowing capacity on a heater, it is possible to define, what temperature will be in this case on a surface ostekleniya.

In the second series of experiments heating of a cold interglass interval, for this purpose a double-glazed window was conducted established from a warm premise, and unary osteklenie — from the cold party. Comparison of distribution of temperatures on height ostekleniya from a premise at heating of various air layers at the same capacity of a thermal emission (50 Vt/m) has shown, that at a thermal emission in a thermal air layer the temperature internal ostekleniya has appeared more than on 4°S above, than at heating of a cold air layer.

Comparison of distributions of thermal streams to the warm and cold party at thermal emissions in various layers at threefold osteklenii is shown on fig. 4.

Comparison shows, that at heating of a warm air layer thermal streams both with warm and from the cold party of a window it is less, than at a thermal emission in a cold air layer. It testifies that productivity of heat of a heater above at heating of a thermal air layer.

In summary it is necessary to notice, that at a thermal emission in air layers three-layer ostekleniya along with increase in temperature internal ostekleniya, its more uniform distribution on a surface ostekleniya, reduction of losses from a premise, the general thermal losses including a part of heat of a heater, leaving on street, grow with increase in capacity of thermal emissions. To reduce the general thermal losses and to strengthen effect of growth of temperature internal ostekleniya use together with a thermal emission in air layers special teplootrazhayuschih covers on glasses allows.

In the third series of experiments experiments of the first series have been repeated, but the usual double-glazed window has been replaced with a double-glazed window with teplootrazhayuschim cover which has been put on a surface has flown down from the interior of a double-glazed window. The given cover executed on the basis of silver by a vacuum dusting, passes to 80 % of energy in a visible range and reflects to 95 % in the infra-red.

In drawing 5 comparison of reduction relative teplopoter from a premise through threefold osteklenie is resulted at heating

Dq/qo = (qo–q)/qo

On height ostekleniya from the warm party at identical loads on a heater, 100 Vt/m, for a double-glazed window with cover and without cover. In drawing it is accepted qo — density of a thermal stream without heating, q — density of a thermal stream with heating. From drawing it is visible, that at heating for the first variant i.e. when it is used threefold osteklenie without teplootrazhayuschego covers, relative reduction of thermal losses is less, than at a variant threefold ostekleniya with application teplootrazhayuschego covers. It means that productivity of energy of a heater above at use teplootrazhayuschego covers.

Thus, as a result of the conducted experimental researches it is established:
  • For threefold ostekleniya at thermal emissions per unit of length of a bottom edge ostekleniya 50-100 Vt/m in the bottom part of the interglass air interval possessed more close to a warm premise, were observed substantial increase of temperature of the bottom zone ostekleniya from a premise.
  • Average time of an exit of temperature ostekleniya on a stationary mode at a thermal emission in the bottom part of an interglass air interval at load made of 50 Vt/m about one hour, and level achievement in 90 % from this temperature occurred for the first half an hour.
  • At multilayered osteklenii most effectively also is economically justified to conduct heating of the bottom part of the air interval nearest from a warm premise.
  • At application teplootrazhayuschego covers at threefold osteklenii it is observed bolshiy a positive effect from heating of interglass space, than without cover.
Source: the Newspaper "Building" #47 heading «Stroyinform»

It is introduced: on December, 23rd, 2002

Eksperimentalnoe research of heating of interglass space at threefold osteklenii

For maintenance of comfortable conditions indoors it is necessary, that difference of temperatures between air temperature indoors and temperature of internal surfaces of protecting designs was minimum. The lowest during the winter period of time indoors usually is the surface temperature ostekleniya windows that creates discomfortable zones near to them. Therefore actual the problem of working out and research of new designs of windows with more heats of an internal surface ostekleniya is represented.

In connection with icrease of requests to resistance to a heat transfer svetoprozrachnyih protecting designs in the conditions of a city of Tomsk for residential buildings the resulted resistance to a heat transfer for windows and balcony doors should be not less than 0,64 m І • ° With/vt. At the same time resistance to a heat transfer for threefold ostekleniya in wooden or plastic covers makes 0,55 m І • ° With/vt. Thus, for fulfilment of existing standard requests for conditions of a city of Tomsk it is necessary to pass to other kinds of window fillings, that, as a rule, reduces svetopropuskanie, complicates a design of a window and increases its cost.

One of effective methods of rise in temperature internal ostekleniya is electric heating of windows. Variants of use electrowarmed ostekleniya which is especially effective together with application teplootrazhayuschih covers are known. There are data of tests of electric heating of an interglass air interval at double osteklenii. In the given work results of an experimental research of influence of a thermal emission in interglass space on temperatures of surfaces ostekleniya and resistance to a window heat transfer are presented at threefold osteklenii.

Experiments are conducted in the climatic chamber. The tested fragment ostekleniya represented a single-chamber double-glazed window (a thickness of an air layer — 16 mm, a thickness of glasses — 4 mm) and unary osteklenie in the thickness of 6 mm established in the general frame. The distance between a double-glazed window and unary ostekleniem made 57 mm. The sizes ostekleniya were 325h825 mm І. In the centre of an air interval between a double-glazed window and unary ostekleniem on all width of a window in the bottom part at height of 20 mm from a bottom edge ostekleniya have been established a cylindrical ohmic heater. In experiences the thermal stream made through a heater per unit of length of a bottom edge ostekleniya, was changed from 27 to 100 Vt/m. Temperature in cold branch of the climatic chamber during realisation of experiments was-35°S, in warm branch +18°S.

The field of local thermal streams on a glass surface was measured by gauges of thermal streams, temperatures of glasses in various points of a surface were defined by the microthermocouples established on an internal and outside surface of a window.

In the basic series of experiments the double-glazed window has been established from cold branch of the climatic chamber. Distributions of temperatures and density of thermal streams for various capacities of thermal emissions in a thermal air layer are received. As a result of realisation of experiments it has been established, that the above load on a heater, the the temperature ostekleniya is more considerably lifted. More essential rise in temperature on a surface ostekleniya was observed from a premise, is closer to which the heater (fig. 1,) is established. Smaller influence heating on temperature external ostekleniya (rendered fig. 1,).

Thus, during experiments it has been established, that at small thermal emissions of 50-100 Vt/m in the bottom part of an air layer at three-layer osteklenii, it is possible to achieve essential rise in temperature of internal glass in the bottom zone and to create more uniform distribution of temperatures on height ostekleniya from a premise.

Measurements of thermal streams from the warm and cold parties of a window are conducted at different capacities of heating. From the executed measurements the thermal stream leaving through osteklenie from a premise follows, that with increase in capacity of thermal emissions, decreases, that is connected with decrease in difference of temperatures between temperature ostekleniya and air temperature indoors.

With increase in the capacity submitted on a heater, resistance to a heat transfer of a design "double-glazed window-glass" which was defined by standard image has increased: the relation of a difference of temperatures between temperatures of internal and outside air to the density of a thermal stream going from a premise through osteklenie. So, without heating resistance to a heat transfer of the given design for standard conditions (at factors of a heat transfer from internal and outside surfaces of 8,2 and 23 Vt/m І • ° With accordingly) made 0,56 m І • ° With/vt, at load on a heater of 27 Vt/m — 0,77 m І • ° With/vt, and at 50 Vt/m — 1,02 m І • ° With/vt.

Change of temperature in the bottom zone ostekleniya, at different capacities of load of a heater, with the course of time from the beginning of work of a heater is shown on fig. 2. For temperature of the bottom zone ostekleniya the temperature which the thermocouple established on osteklenii above its bottom edge on 100 mm showed started. From drawing follows, that the the big capacity we submit on a heater, the it is required to more time for a temperature exit ostekleniya on an equilibrium condition. At a mode of heating time of an exit for a stationary mode made of 50 Vt/m the little more than 60 mines, and level achievement in 90 % from equilibrium temperature occurred within the first 30 minutes

On fig. 3 approximating dependence of results of the conducted experiments, showing is resulted, what maximum rise in temperature on an internal surface of glass occurs owing to giving of this or that electric capacity on a heating element. On this drawing it is possible to determine the size capacities which is necessary for submitting on a heater for maintenance of the required temperature on a surface ostekleniya in the bottom zone and, on the contrary, knowing capacity on a heater, it is possible to define, what temperature will be in this case on a surface ostekleniya.

In the second series of experiments heating of a cold interglass interval, for this purpose a double-glazed window was conducted established from a warm premise, and unary osteklenie — from the cold party. Comparison of distribution of temperatures on height ostekleniya from a premise at heating of various air layers at the same capacity of a thermal emission (50 Vt/m) has shown, that at a thermal emission in a thermal air layer the temperature internal ostekleniya has appeared more than on 4°S above, than at heating of a cold air layer.

Comparison of distributions of thermal streams to the warm and cold party at thermal emissions in various layers at threefold osteklenii is shown on fig. 4.

Comparison shows, that at heating of a warm air layer thermal streams both with warm and from the cold party of a window it is less, than at a thermal emission in a cold air layer. It testifies that productivity of heat of a heater above at heating of a thermal air layer.

In summary it is necessary to notice, that at a thermal emission in air layers three-layer ostekleniya along with increase in temperature internal ostekleniya, its more uniform distribution on a surface ostekleniya, reduction of losses from a premise, the general thermal losses including a part of heat of a heater, leaving on street, grow with increase in capacity of thermal emissions. To reduce the general thermal losses and to strengthen effect of growth of temperature internal ostekleniya use together with a thermal emission in air layers special teplootrazhayuschih covers on glasses allows.

In the third series of experiments experiments of the first series have been repeated, but the usual double-glazed window has been replaced with a double-glazed window with teplootrazhayuschim cover which has been put on a surface has flown down from the interior of a double-glazed window. The given cover executed on the basis of silver by a vacuum dusting, passes to 80 % of energy in a visible range and reflects to 95 % in the infra-red.

In drawing 5 comparison of reduction relative teplopoter from a premise through threefold osteklenie is resulted at heating

Dq/qo = (qo–q)/qo

On height ostekleniya from the warm party at identical loads on a heater, 100 Vt/m, for a double-glazed window with cover and without cover. In drawing it is accepted qo — density of a thermal stream without heating, q — density of a thermal stream with heating. From drawing it is visible, that at heating for the first variant i.e. when it is used threefold osteklenie without teplootrazhayuschego covers, relative reduction of thermal losses is less, than at a variant threefold ostekleniya with application teplootrazhayuschego covers. It means that productivity of energy of a heater above at use teplootrazhayuschego covers.

Thus, as a result of the conducted experimental researches it is established:
  • For threefold ostekleniya at thermal emissions per unit of length of a bottom edge ostekleniya 50-100 Vt/m in the bottom part of the interglass air interval possessed more close to a warm premise, were observed substantial increase of temperature of the bottom zone ostekleniya from a premise.
  • Average time of an exit of temperature ostekleniya on a stationary mode at a thermal emission in the bottom part of an interglass air interval at load made of 50 Vt/m about one hour, and level achievement in 90 % from this temperature occurred for the first half an hour.
  • At multilayered osteklenii most effectively also is economically justified to conduct heating of the bottom part of the air interval nearest from a warm premise.
  • At application teplootrazhayuschego covers at threefold osteklenii it is observed bolshiy a positive effect from heating of interglass space, than without cover.
Source: the Newspaper "Building" #47 heading «Stroyinform»

It is introduced: on December, 23rd, 2002

Eksperimentalnoe research of heating of interglass space at threefold osteklenii
For maintenance of comfortable conditions indoors it is necessary, that difference of temperatures between air temperature indoors and temperature of internal surfaces of protecting designs was minimum. The lowest during the winter period of time indoors usually is the surface temperature ostekleniya windows that creates discomfortable zones near to them. Therefore actual the problem of working out and research of...
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