Hot Beverage Outlet Geometry for Bubble-Free Dispensing
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Solution Overview
Problem
Existing hot beverage preparation devices, such as espresso machines, often form large air bubbles that interfere with even distribution and continuous outflow of coffee, leading to blocked outlets and compromised crema quality.
Innovation Solution
A hot beverage preparation device with a beverage outlet featuring partial outlets with a monotonically increasing flow cross section, including stepped enlargements, and compensation chambers for phase separation and pressure equalization, which prevents bubble formation and maintains crema quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional outlet geometry is used, then device complexity is low, but large air bubbles form that block outflow openings and prevent continuous liquid outflow
Solution Approach 1:
The outlet is divided into multiple partial outlets (typically two) instead of a single outlet, allowing the liquid flow to be split into separate streams. This segmentation prevents bubble accumulation and blocking at a single opening while maintaining simple overall device geometry.
Solution Approach 2:
Each partial outlet is designed with a monotonically increasing flow cross-section, creating locally optimized flow conditions. The cross-sectional area increases from the inlet toward the outlet opening, ensuring smooth liquid flow and preventing bubble formation at critical locations without requiring complex overall device redesign.
2Manufacturing precision
If stepped enlargements are added to partial outlets, then bubble destruction and crema quality improve, but manufacturing complexity increases
Solution Approach 1:
The flow cross-section parameters of the partial outlets are systematically changed by introducing stepped enlargements. These steps create controlled turbulence and pressure changes that destroy large bubbles and generate fine-bubble crema, while the geometric changes remain simple enough for standard manufacturing processes.
3Manufacturing precision
If flow cross section is reduced at outlet openings, then liquid distribution improves, but pressure increases that adversely affect crema consistency
Solution Approach 1:
Instead of reducing the flow cross-section at the outlet opening to improve distribution, the design inverts the approach by monotonically increasing the cross-section from inlet to outlet. The distribution control is achieved through the splitting into multiple partial outlets rather than constriction, thereby avoiding pressure increases that would harm crema quality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures a bubble-free dispensing of coffee, maintaining crema consistency and quality by bursting large bubbles and preventing pressure increases, while using a simple and easy-to-manufacture geometry.
Implementation Method 1
the increase in the flow cross section can be continuous, but advantageously takes place in steps... it is avoided that the flow cross section becomes smaller, at least as long as there is no atmospheric pressure, since this would lead to an increase in pressure due to the inflowing liquid
Implementation Method 2
The surface tension in the front area of the bubble envelope gradually increases, the further the bubble is pushed forward by the flowing liquid. Until the shell can no longer withstand the tension and the bubble bursts.
Implementation Method 3
Phase separation of the prepared beverage takes place in the first compensation chamber... the liquid can accumulate in front of the outlet opening... the individual phases separate due to their difference in density and the resulting different buoyancy forces
Data Source
Figure 1
AI summary
A hot beverage preparation device for household purposes, in particular a fully automatic coffee machine, is described. It comprises an outlet (1), which includes an inlet (2) and a number of partial outlets (3). The partial outlets (3) fluidically connect the inlet (2) with a respective partial outlet opening (4). In addition, the partial outlets (3) each have a monotonically increasing cross section in the direction of their partial outlet opening (4) up to the partial outlet opening (4). The increase (5, 6) of this cross section occurs in particular in steps.