Heat Source Unit Air Passage Design to Reduce Propeller Fan Noise
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Solution Overview
Problem
Conventional heat source units for refrigeration apparatuses generate noise due to varying air flow rates through the outdoor heat exchanger and fan, leading to significant differences in air velocity across different areas, resulting in noise from the propeller fan's rotation.
Innovation Solution
A heat source unit design with a box-shaped casing, a partition plate inside the casing to create an air passage, and a propeller fan positioned to blow air toward the outlet, where the first distance between the fan and the second portion of the heat exchanger and the second distance between the fan and the partition plate satisfy the relationship 6 ≤ S1/S2, with S2 being between 10 mm and 40 mm, to reduce noise by evening out air velocity differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the heat exchanger is positioned close to the fan to improve heat exchange efficiency, then the air flow rate increases, but the air velocity becomes uneven across different areas causing fan noise
Solution Approach 1:
The patent applies local quality by positioning the heat exchanger's first portion closer to the fan (S1 ≤ 40mm) to maximize air flow, while simultaneously positioning the second portion farther from the fan (S2 ≥ 10mm) to prevent excessive air velocity. This differential positioning creates localized optimization: the first portion captures air efficiently while the second portion acts as a flow dampener, reducing velocity variations across the fan surface and minimizing noise generation.
2Object-generated harmful factors
If the heat exchanger is positioned far from the fan to reduce air velocity differences, then fan noise decreases, but the air flow rate and heat exchange efficiency are reduced
Solution Approach 1:
The patent segments the heat exchanger into two distinct portions with different positioning strategies. The first portion (61) is positioned close to the fan to maintain high air flow rate, while the second portion (62) is positioned farther away to reduce air velocity. This segmentation allows each portion to fulfill different functions: the first portion maximizes heat exchange efficiency while the second portion controls air velocity to minimize fan noise, thereby resolving the contradiction between productivity and noise reduction.
3Object-generated harmful factors
If the second distance S2 is made very large to equalize air velocity, then fan noise is reduced, but the overall air passage length increases and compactness is lost
Solution Approach 1:
The patent applies parameter changes by establishing specific quantitative relationships for the distances S1 and S2. The second distance S2 is constrained to be at least 10mm but no more than 40mm, and the ratio S1/S2 is set to be 6 or less. These parameter constraints ensure that S2 is sufficiently large to reduce air velocity and minimize fan noise, while simultaneously limiting the overall air passage length to maintain compact design. This quantitative approach resolves the contradiction between noise reduction and compactness.
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
This design effectively reduces noise generated by the propeller fan's rotation by minimizing air velocity differences across the heat exchanger, resulting in lower sound power levels, particularly at 125 Hz, as demonstrated by experimental graphs showing decreased sound power levels with optimized distance ratios and second distance settings.
Implementation Method 1
a propeller fan (70) provided in the air passage (A) to blow air toward the outlet (52) of the casing (50)
Implementation Method 2
a heat exchanger (60) provided in the air passage (A) and having a first portion (61) along the back surface of the casing (50) and a second portion (62) along the one side surface of the casing (50)
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A heat source unit (3) for a refrigeration apparatus (1) includes a casing (50), a heat exchanger (60), and a propeller fan (70). The casing (50) has a back surface and one side surface each having an inlet (53), and a front surface having an outlet (52). A partition plate (51) defining an air passage (A) faces the one side surface of the casing (50). The heat exchanger (60) is provided along the inlet (53). A first distance S1 and a second distance S2 satisfies the relationship "6 ≤ S1/S2," where the first distance S1 is the shortest distance between an outer peripheral circle (V) of the propeller fan (70) and a second portion (62) of the heat exchanger (60), and the second distance S2 is the shortest distance between the outer peripheral circle (V) of the propeller fan (70) and the partition plate (51).