## 5 Conclusions  
The performance of an adsorption heat pump using MSC-30/R1234 yf pair was investigated using an improved model that accounts for the impact of thermal masses. The adsorption isotherms of the selected working pair were measured using the constant-volume-variable-pressure apparatus in the temperature range from 20 \({}^{\circ}\)C to 70 \({}^{\circ}\)C starting from a very low pressure of around 0.01 kPa. The performance of the heat pump was compared with MSC-20/R134a pair using the published data. The isotherm data were fitted using various adsorption isotherm models of Type I. It was observed that the D-A model with the volume correction and Toth model provide the best fit, typically below 3% of the fitting error. The improved equilibrium model was selected to supplement the current experimental findings as the references often offer the performance evaluation while neglecting the influence of the thermal masses of heat exchangers. The influence of the thermal mass on the equilibrium cycle was investigated for the ratios in the range from 0 to 3 of the heat exchanger to the adsorbent material.  
The presented SHP values of MSC-30/R1234 yf are substantially lower than those of the MSC-30/R134a pair under the same temperature conditions. We have shown how the effect of thermal mass is significant for the desorption (regeneration) temperatures. MSC-30/R134a pair offers better performance in the selected desorption temperature range, and the gap in the performance between MSC-30/R1234 yf is increasing with increasing temperature. We have also shown that the COP of the MSC-30/R1234 yf pair is around 0.05 to 0.35 at the selected desorption temperature range considering only the adsorbent thermal mass. Under the same conditions, MSC-30/R134a pair offers approximately 0.1 to 0.6 COP for the heating application. Furthermore, considering the highest thermal mass ratio of 1:3, the COP can be effectively reduced by half of its value in both cases. Despite a relatively  
Figure 12: COP for heating application of MSC-30/R1234 yf, volume correction \(\alpha=1/\)T[K].  
poor performance, R1234 yf has negligible GWP as compared to the target replacement, i.e., R134a. The present isotherm will be essential for the development of automobile heat pump systems, especially for the direct hybridization using a single refrigerant.  
The following are available online at [[https://www.mdpi.com/2076-3417/11/5/2279/s1](https://www.mdpi.com/2076-3417/11/5/2279/s1)]([https://www.mdpi.com/2076-3417/11/5/2279/s1](https://www.mdpi.com/2076-3417/11/5/2279/s1)), Table S1: The parameters of the [PERSON] model (Equation (9))--MSC-30/R134a experimental data from [29]. Table S2: The parameters of the Langmuir and the Toth model (Equations (10)-(13))--MSC-30/R134a experimental data from [29]. Table S3: The parameters of the D-R model (Equation (14))--MSC-30/R134a experimental data from [29]. Table S4: The parameters of the D-A model (Equations (15) and (16))--MSC-30/R134a experimental data from [29].  
Writing and original draft preparation, Data analysis, S.S.; Investigation, Y.M. and K.T.; Methodology, K.T.; Writing--review and editing, F.M. and K.T.; Review and editing, T.M. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Data available statement: Data is contained within the article or supplementary material.  
The authors declare