Circulation pump control with control algorithm for speed control depending on the Reynolds number
The pump system with a control algorithm adjusts pump power to maintain the Reynolds number between 2320 and 4000, addressing inefficiencies in heat transfer systems by balancing energy consumption and heat transfer.
Patent Information
- Application Number
- DE202025002842
- Authority / Receiving Office
- DE · DE
- Patent Type
- Utility models
- Current Assignee / Owner
- Filing Date
- 2025-09-26
- Publication Date
- 2026-01-08
- Estimated Expiration
- 2035-09-30
AI Technical Summary
Existing heat transfer systems face inefficiencies due to either high energy consumption in turbulent flow or inadequate heat transfer in laminar flow, with the optimal balance occurring in the transition range between 2320 and 4000 Reynolds number, necessitating a control mechanism to maintain this range.
A control algorithm integrated into the pump system adjusts the pump power based on the Reynolds number to regulate flow within the optimal range, using a speed controller and external sensors to manage volume flow rate and pressure loss.
This approach optimizes energy efficiency and heat transfer by maintaining the flow in the transition range, balancing pressure loss and heat transfer performance.
Smart Images
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Abstract
Description
[0001] In many heat transfer applications, it is important to know whether the flow of the heat transfer medium is laminar or turbulent. Especially in ground-source heat pumps, the flow pattern of the heat transfer medium – usually a water-glycol mixture – plays a crucial role in the efficiency of the heat transfer.
[0002] As a general rule, turbulent flow is preferred when maximum heat transfer is the goal. The intensive mixing of the medium reduces temperature gradients within the flow, significantly improving heat transfer between the ground and the medium. The turbulence ensures that heat is not only absorbed at the pipe wall but also quickly transferred into the medium – a clear advantage when extracting geothermal energy.
[0003] However, this efficiency comes at a price: Turbulent flow (Re > 4000) causes higher pressure losses, meaning the circulation pump requires more energy to move the medium through the collectors. This can significantly increase the system's electricity consumption and thus worsen the overall efficiency – especially in poorly designed systems or with long pipelines.
[0004] Alternatively, there is laminar flow (Re < 2320), in which the medium flows in parallel layers. This is more energy-efficient because the pressure loss is low and the pump has to work less. However, heat transfer is significantly worse because there is no mixing and the heat is transported slowly from the pipe to the flow. This can lead to inefficient use of the ground, especially with high heating loads.
[0005] The optimal solution often lies in the transition range, i.e., a flow with a Reynolds number between 2320 and 4000. In this range, a good compromise between heat transfer performance and pump energy consumption can be achieved. The flow is not completely turbulent, but neither is it strictly laminar – it offers a degree of mixing with moderate pressure loss.
[0006] The invention specified in claim 1 is based on the idea of integrating a control algorithm into the pump or pump control system, which determines the Reynolds number of the flow and controls the pump power in such a way that the flow remains in the boundary range between laminar and turbulent.
[0007] To regulate the pump, for example in a ground collector system, to an optimal Reynolds number, the speed of the pump must be changed so that the volume flow rate changes.
[0008] The pump and speed control system is characterized by the fact that the pump motor is controlled by a speed controller, e.g., a frequency converter, which is placed internally in or externally outside the pump, and regulates the volume flow.
[0009] The flow rate is determined either internally from pump data or externally using a flow meter or a heat meter with a flow rate display. Based on the specified pipe dimensions and brine properties (type, concentration, viscosity), the Reynolds number is calculated, and the target flow rate is adjusted accordingly to remain within the setpoint range. A temperature-dependent correction using a media temperature sensor is advisable but not strictly necessary. However, the viscosity of the brine changes with temperature. At lower temperatures, the viscosity increases, and the Reynolds number decreases. Therefore, a higher pump output may be required to maintain the target flow rate.
[0010] The volume flow rate can be controlled by connecting an external system controller. This allows a decision to be made as to whether the flow rate takes priority or whether the limits of the flow range (here, the transition range) must be observed.
[0011] The control parameters are set via a suitable user interface on the pump / pump controller or via an external signal (e.g., BUS) from the system controller. This allows the pump output to be linked to, for example, the outside temperature or the heating load.
[0012] In addition to manual adjustment of the control parameters, the pump control system can independently and iteratively determine the Reynolds number limit by varying the pump speed and identifying when the slope of the pressure loss coefficient changes significantly. This speed or flow rate range is then used as the limit of the control range and processed by the control system to ensure the pump operates within the desired flow range. Formula understanding: Reynolds number
[0013] In pipe flows, the characteristic quantities usually used are the inner diameter d, the velocity averaged over the cross-section v and the kinematic viscosity of the fluid v.
[0014] The Reynolds number (Re) is calculated according to: Re=d×vν • v: mean flow velocity • d: Pipe diameter • v: kinematic viscosity
[0015] Since v (volume flow rate divided by cross-sectional area), the Reynolds number can be directly influenced via the volume flow rate Q - and thus via the pump speed. List of designations 1 pump 2 Pump controllers (internal or external) 3 Pipeline 4 User Interface (optional) 5 BUS connection (optional) 6 Volume flow sensor (optional) 7 Temperature sensor (optional) 8 * = optional
Claims
[1] A circulating pump with internal or external control, with or without a user interface, with or without bus or other control, with or without a flow sensor, with or without a temperature sensor is equipped with a control algorithm that determines the Reynolds number of the flow and controls the pump power so that the flow remains in the boundary range between laminar and turbulent. [2] Circulating pump with internal or external control and algorithm according to claim 1 characterized by that the flow remains in the laminar range. [3] Circulating pump with internal or external control and algorithm according to claim 1 characterized by that the flow remains in the turbulent range. [4] Circulating pump with internal or external control and algorithm according to claim 1 characterized by , that it is freely selectable in which area the flow should remain. [5] Circulating pump with internal or external control and algorithm according to claim 1 characterized by that the pump control independently and iteratively determines the limit of the Reynolds number and adopts this as the limit of the control range.