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Town central vacuumation systems
628
Letters to the Editors REFERENCES
BEEBER. G. (1967) Changes in visibility restrictions over a 20 year period, Buff. Am. met. Sec. 48,348.
HOUWORTH G. C. (1962) Some effects of air pollution on visibility in and near cities. Symposium, Air over Cities, SEC Technical Report A62-5, Public Health Service, R. A. Taft Sanitary Engineering Center, Cincinnati, Ohio. MANUALOF OBSERVATIONS (1961) Circular N, p. 23, 7th Edn., US. Govt. Printing Office. MCCORMICK R. A. and LWDW~G J. H. (1967) Climatic modification by atmospheric aerosols. Science 156, 1358-1359. STEFFENSC. (1956) Visibility and air pollution. Air Pollution Handbook,MA~~LL,and ACKLEY(Eds.) McGraw-Hill, New York.
TOWN CENTRAL
VACUUMATION
SYSTEMS
(Received 14 August 1968) CONSIDERABLE improvement of the quality of urban air could be effected by the provision of a facility for the immediate disposal of household wastes, as a replacement of the present system whereby such refuse may stand in bins for a week or more. Sink disposal units already provide one means of managing this removal, but these are limited to waste food. Fast running water would be necessary to remove large or dense objects, providing a problem in the provision and disposal of such a large volume of water, while a separate removal system would still be necessary for bulky objects. An alternative is a whole town central vacuumation system fWr~LI[Ak-fs,1%7)-a logical deveiopment of the systems already functioning with great advantages in many ~arge.buil~n~. Such a system was designed for the new community of Cumbemauld in Scotland, by B.V.C. Engineering Limited, of Leatherhead in Surrey, to provide for combined refuse removal and cleaning of internal spaces of dust by means of vacuum power from a central extractor plant. A pilot scheme is already in operation in Sweden at Sundbyberg near Stockholm. This was installed by AB Central Sug and carries waste from 1200 apartments to an incinerating plant 1500 m away. The main di~d~ntage of such a system is the high capital outlay. Upkeep for the plant is expected to be very low, however, and with labour costs continually rising, a saving might even be effected over a long period. K. W. FLITCROFT
13 Berkentaan, Antwerp, Belgium. REFERENCES
WILLIAMSA. F. (1967) Automatic refuse disposal by vacuum. Automation (June issue). AB CENTRALSue (1968) Vacuum sealed refuse canveyanfe in reside~ti~f areas.
THERMAL
ROUGHNESS
RECENTmeasurements, e.g. KAIMALet al. (1967), PASQUILL(lY67), MOORE(1967), indicates that at heights above 150 m large amplitude atmospheric turbulence in winds up to 10 m. set-r is largely thermal in origin. It would appear, therefore, for effects above 150 m, that the surface should be described in thermal terms, rather than by a “roughness length”. Convenient thermal parameters would be the amplitude of temperature differences and the “wavelength” of these differences. Infrared line scan pictures taken from aircraft in which the optical density of the negative is a measure of the true surface temperature, provide a convenient means of assessing these “thermal roughness” parameters.
Letters to the Editors REFERENCES
BEEBER. G. (1967) Changes in visibility restrictions over a 20 year period, Buff. Am. met. Sec. 48,348.
HOUWORTH G. C. (1962) Some effects of air pollution on visibility in and near cities. Symposium, Air over Cities, SEC Technical Report A62-5, Public Health Service, R. A. Taft Sanitary Engineering Center, Cincinnati, Ohio. MANUALOF OBSERVATIONS (1961) Circular N, p. 23, 7th Edn., US. Govt. Printing Office. MCCORMICK R. A. and LWDW~G J. H. (1967) Climatic modification by atmospheric aerosols. Science 156, 1358-1359. STEFFENSC. (1956) Visibility and air pollution. Air Pollution Handbook,MA~~LL,and ACKLEY(Eds.) McGraw-Hill, New York.
TOWN CENTRAL
VACUUMATION
SYSTEMS
(Received 14 August 1968) CONSIDERABLE improvement of the quality of urban air could be effected by the provision of a facility for the immediate disposal of household wastes, as a replacement of the present system whereby such refuse may stand in bins for a week or more. Sink disposal units already provide one means of managing this removal, but these are limited to waste food. Fast running water would be necessary to remove large or dense objects, providing a problem in the provision and disposal of such a large volume of water, while a separate removal system would still be necessary for bulky objects. An alternative is a whole town central vacuumation system fWr~LI[Ak-fs,1%7)-a logical deveiopment of the systems already functioning with great advantages in many ~arge.buil~n~. Such a system was designed for the new community of Cumbemauld in Scotland, by B.V.C. Engineering Limited, of Leatherhead in Surrey, to provide for combined refuse removal and cleaning of internal spaces of dust by means of vacuum power from a central extractor plant. A pilot scheme is already in operation in Sweden at Sundbyberg near Stockholm. This was installed by AB Central Sug and carries waste from 1200 apartments to an incinerating plant 1500 m away. The main di~d~ntage of such a system is the high capital outlay. Upkeep for the plant is expected to be very low, however, and with labour costs continually rising, a saving might even be effected over a long period. K. W. FLITCROFT
13 Berkentaan, Antwerp, Belgium. REFERENCES
WILLIAMSA. F. (1967) Automatic refuse disposal by vacuum. Automation (June issue). AB CENTRALSue (1968) Vacuum sealed refuse canveyanfe in reside~ti~f areas.
THERMAL
ROUGHNESS
RECENTmeasurements, e.g. KAIMALet al. (1967), PASQUILL(lY67), MOORE(1967), indicates that at heights above 150 m large amplitude atmospheric turbulence in winds up to 10 m. set-r is largely thermal in origin. It would appear, therefore, for effects above 150 m, that the surface should be described in thermal terms, rather than by a “roughness length”. Convenient thermal parameters would be the amplitude of temperature differences and the “wavelength” of these differences. Infrared line scan pictures taken from aircraft in which the optical density of the negative is a measure of the true surface temperature, provide a convenient means of assessing these “thermal roughness” parameters.