{"id":92682,"date":"2025-03-18T10:24:22","date_gmt":"2025-03-18T10:24:22","guid":{"rendered":"https:\/\/www.valrom.ro\/calculation-algorithm-pressure-drop-flow-under-pressure\/"},"modified":"2025-09-02T11:37:45","modified_gmt":"2025-09-02T11:37:45","slug":"calculation-algorithm-pressure-drop-flow-under-pressure","status":"publish","type":"page","link":"https:\/\/www.valrom.ro\/en\/calculation-algorithm-pressure-drop-flow-under-pressure\/","title":{"rendered":"Calculation algorithm PRESSURE DROP – FLOW UNDER PRESSURE"},"content":{"rendered":"

PRESSURE DROP – FLOW UNDER PRESSURE<\/h3><\/div>
Calculation of pressure pipe flow pressure drop using the Darcy-Weisbach-Colebrook equation<\/h6><\/div>

The shear stress due to the viscosity of the fluid and the friction force at the pipe wall create a resistance to flow, expressed as a pressure loss and expressed in meters (of pipe).
The calculation is done with the Darcy-Weisbach\/Colebrook formula, which has the following form:<\/p>\n

    \n
  • h: load drop [m]<\/li>\n
  • f: friction factor (dimensionless, depends on surface roughness and flow regime<\/li>\n
  • L: flow length [m]<\/li>\n
  • v: flow velocity [m\/s]<\/li>\n
  • d: flow diameter (inner diameter of the pipe) [m]<\/li>\n
  • g: gravitational acceleration [m\/s2<\/sup>]<\/li>\n<\/ul>\n

    Flow velocity [m\/s] is calculated from the flow rate and the flow section<\/p>\n

      \n
    • Q: flow rate [m3<\/sup>\/s]<\/li>\n
    • d: flow diameter (inner diameter of the pipe) [m]<\/li>\n<\/ul>\n

      The friction factor is dependent on the flow regime: laminar (Re\u22642000), turbulent (Re\u22654,000) or transient.<\/p>\n

      The flow regime is determined by the Reynolds number:<\/p>\n

        \n
      • Re: Reynolds number, dimensionless<\/li>\n
      • \u03c1: density [kg\/m3<\/sup>]\u201d<\/li>\n
      • v: flow velocity [m\/s]<\/li>\n
      • d: flow diameter (inner diameter of the pipe) [m]<\/li>\n
      • eta: dynamic viscosity [kg\/m\u00d7s]<\/li>\n<\/ul>\n

        Dynamic viscosity (\u03b7) is a property of a fluid, measured in [kg\/m*s] and is temperature dependent.<\/p>\n

        For laminar regime:<\/p>\n

         <\/p>\n

        For turbulent regime (Colebrook formula):<\/p>\n

          \n
        • \u03b5: roughness [m]<\/li>\n
        • Re: Reynolds number, dimensionless<\/li>\n<\/ul>\n

          Some typical roughness values \u200b\u200b[m] for the main materials used in pipe construction:<\/p>\n\n\n\n\n\n\n\n\n\n\n
          Material<\/td>\nValue<\/td>\n<\/tr>\n<\/thead>\n
          Plastic<\/td>\n0.01\u00d710-3<\/sup><\/td>\n<\/tr>\n
          Asbestos<\/td>\n0.1\u00d710-3<\/sup><\/td>\n<\/tr>\n
          Steel<\/td>\n0.2\u00d710-3<\/sup><\/td>\n<\/tr>\n
          Cast iron<\/td>\n0.5\u00d710-3<\/sup><\/td>\n<\/tr>\n
          Concrete<\/td>\n1\u00d710-3<\/sup><\/td>\n<\/tr>\n
          Steel (rusty)<\/td>\n2\u00d710-3<\/sup><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

          For transient regimes, the Darcy friction factor cannot be calculated with acceptable accuracy and the algorithm does not apply.<\/p>\n

          Note: Pressure loss [kg\/m\u00d7s or Pa] is calculated from the pressure loss with the formula: \u0394p = \u03c1gh<\/b><\/p>\n

            \n
          • \u03c1: density, [kg\/m3<\/sup>]<\/li>\n
          • g: gravitational acceleration. [m\/s2<\/sup>] <\/li>\n
          • h: load loss. [m] <\/li>\n<\/ul>\n
            (*) sources<\/em><\/div>\n
            Handbook of PE pipe, plasticpipe.org, capt. 6, pag. 169; <\/em><\/div>\n
            wikipedia.org (http:\/\/en.wikipedia.org\/wiki\/Darcy\u2013Weisbach_equation)<\/em><\/div>\n<\/div><\/div><\/div><\/div><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":3,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"100-width.php","meta":{"inline_featured_image":false,"footnotes":""},"class_list":["post-92682","page","type-page","status-publish","hentry"],"yoast_head":"\nCalculation algorithm PRESSURE DROP - FLOW UNDER PRESSURE - Valrom Industrie<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.valrom.ro\/en\/calculation-algorithm-pressure-drop-flow-under-pressure\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Calculation algorithm PRESSURE DROP - FLOW UNDER PRESSURE\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.valrom.ro\/en\/calculation-algorithm-pressure-drop-flow-under-pressure\/\" \/>\n<meta property=\"og:site_name\" content=\"Valrom Industrie\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/ValromIndustrie\/\" \/>\n<meta property=\"article:modified_time\" content=\"2025-09-02T11:37:45+00:00\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"5 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.valrom.ro\\\/en\\\/calculation-algorithm-pressure-drop-flow-under-pressure\\\/\",\"url\":\"https:\\\/\\\/www.valrom.ro\\\/en\\\/calculation-algorithm-pressure-drop-flow-under-pressure\\\/\",\"name\":\"Calculation algorithm PRESSURE DROP - 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