A Novel Oil-free Dual Piston Compressor Driven by a Moving Coil Linear Motor with Capacity Regulation Using R134a

Round 1

Reviewer 1 Report

At the end of the introduction the authors explain that the experimental researches are lacked in the air-conditioning sector. However the application of the investigated dual piston compressor seem to be referred to household refrigerators. The authors could clarify the application field considered in the paper.

Author Response

Dear Reviewer:

Thank you very much for the helpful comments and criticisms on our manuscript (sustainability-1151036) entitled '' A novel oil-free dual piston compressor driven by a moving coil linear motor with capacity regulation using R134a ''. According to your recommendations, we have revised carefully our manuscript. The following is a detailed list of response to all comments and criticisms, and changes which the authors have made.

 

Point 1: At the end of the introduction the authors explain that the experimental researches are lacked in the air-conditioning sector. However the application of the investigated dual piston compressor seem to be referred to household refrigerators. The authors could clarify the application field considered in the paper.

Response 1: Thank you for your helpful suggestion.

From my literature, the experiment research on single piston linear compressor for air conditioning (with oil) was only carried out by Lee et al in 2004, the research on oil-free dual piston linear compressor for air conditioning almost can not be found, so the research on dual piston linear compressor for air conditioning is innovative.

A large number of mechanical springs is installed in the single piston linear compressor for air conditioning in order to resist piston offset, which increases the volume, weight and cost of single piston linear compressors. The dual piston linear compressor has no piston offset, which could be an excellent structure for the conditions with large difference in suction pressure and discharge pressure such as air conditioning and refrigerator conditions.

The cooling performance of the dual piston linear compressor is demonstrated in Section 5 in practical air-conditioning condition (evaporation temperature is 10℃，and condensation temperature is 45℃) and ASHRAE-T air conditioning condition (evaporation temperature is 7.2℃, and condensation temperature is 54.4℃). Compared with the commercial crank driven reciprocating compressor for air conditioning, the efficiency advantage of the dual piston linear compressor for air conditioning is proved.

The larger the difference between discharge pressure and suction pressure is, the greater the leakage loss between piston and cylinder is, and the lower the overall efficiency is. The experimental results show that the dual piston linear compressor has a high overall efficiency (the Normalized COP) at the evaporation pressure of 0.35MPa and the condensation pressure of 0.887MPa using R134a. Therefore, the research on the operating characteristics and variable cooling capacity regulation of the dual piston compressor is carried out under the working condition in order to show the high efficiency of the dual piston linear compressor.

Reviewer 2 Report

The topic of linear compressors lacks more research to be extended to existing and new applications and offer to the refrigeration and air conditioning industry oil-less options. There is more research about single linear compressors than dual ones. This paper offers a complete study about a dual compressor, with a full explanation of the methodology and the problem analyzed. My recommendation is to apply minor modifications following these comments.

1. In the Introduction, possible applications for linear compressors (such as electronics cooling) must be commented on. Moreover, the barriers for dual linear compressors in comparison to single ones must be commented on.

2. Propagated uncertainties must be provided in every graphic containing experimental results.

3. Seconds should not appear capitalised (Figure 6. X-axis, time)

4. Why have you selected R134a?

5. Sensors accuracy refers to full-scale range or reading?

6. How do you control subcooling?

7. For "temperature fluctuation of the system is not higher than 0.5K", do you mean plus/minus or absolute?

8. Why have you selected this combination of evaporating and condensing temperatures, in that order?

9. Why the error is at both sides of the 0% line in Figure 11. With heat losses, one part should be always higher than the other.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf