Thermal Analysis of a Forced Flow Diffusion Absorption Refrigeration System for Fishing-Boat Exhaust Waste Heat Utilization

Shuai Du

doi:10.3389/fenrg.2021.761135

Abstract

Ammonia water absorption refrigeration systems are effective in utilizing fishing-boat exhaust waste heat for cryopreservation. However, the liquid level control and the use of a solution pump characterized by small flowrate and high-pressure head result in poor reliability in the traditional system. Besides, the system must necessarily be designed anti-swaying and anti-corrosion. This paper proposes a forced flow diffusion absorption refrigeration system, in which an inherently leak-free canned motor pump and an ejector are employed to provide the driving forces of the gas and liquid loops. The approximate single pressure operation allows for a simple passive liquid sealing control without throttling valves. The system adopts an integrated cooling strategy which allows the system to operate under swaying conditions, and the external seawater cooled heat exchanger avoids internal corrosion and leakage. The thermal analysis shows the system is valid to be operated under wide operating conditions, and the coupled gas and solution circulation ratios determined the performance of the novel system. There is an optimal ammonia mass fraction difference in the gas loop to obtain the optimal COP. The COP reaches 0.4 when the temperatures at the outlets of the generator, evaporator, absorber, and condenser are 160, −15, 35, and 35°C, respectively. The novel system provides a reliable absorption refrigeration system design for fishing-boat applications.

Highlights

Waste heat reuse is quite important to improve primary energy efficiency and the CO2 emission can be reduced effectively (Oluleye et al, 2017)
As x11 − x17 increases, the gas circulation ratio is reduced while the solution circulation ratio is increased; as a result, both the cooling effect and the heat input increase, indicating that the COP depends on the combined effect
In order to solve the drawbacks relating to reliability, antiswaying, and anti-corrosion of modularized ammonia-water absorption refrigeration systems with a cooling capacity of 10kW–50kW applied on fishing-boats for frozen preservation, this paper proposes a forced flow diffusion absorption refrigeration system based on evaporative cooling and adiabatic absorption

Summary

INTRODUCTION

Waste heat reuse is quite important to improve primary energy efficiency and the CO2 emission can be reduced effectively (Oluleye et al, 2017). The novel system adopts an integrated cooling strategy; the condenser and the adiabatic absorber are assembled as one unit, and the condensation heat and the absorption heat are removed by a large amount of precooled solution which is sprayed circularly; the surface area for heat and mass transfer can be ensured even if the system is operated under swaying conditions This strategy uses one external seawater cooled heat exchanger rather than two internal seawater cooled heat exchangers (CON and ABS), and internal corrosion can be avoided and the reliability of the system is improved. As explained in section two that the partial pressure of ammonia changes along the evaporation and absorption processes, there is a mass fraction difference of ammonia in the gas loop, (x11 − x17), which can be assumed first in the calculation. The maximum entrainment ratio can be calculated when PM is equal to P13

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT