Numerical investigation on the operation strategy of a chemisorption heat pump system

ABSTRACT

This paper presents an analysis of the operating characteristics of a chemisorption heat pump. 1-D transient model of a chemisorption heat pump was developed, for which an analysis of four alternating modes of operation was performed. The performance was analyzed with respect to the operating time of the adsorption and desorption operation modes during alternating operations, and the results showed that the cooling capacity has an optimum point depending on the operating times. It was also confirmed that the coefficient of performance increases as the operating time increases. The system performance was also analyzed according to the flow rates of the secondary fluids supplied to the main components. As the flow rates of the secondary fluids supplied to the main components increased, the cooling capacity improved, and the coefficient of performance was found to be compounded by the secondary flow conditions and the operating times of the adsorption and desorption operation modes. Based on the results, it was found that the cooling capacity, coefficient of performance, and specific cooling power of the chemisorption heat pump can be operated in a large range from 876.7 to 3070.0 W, 0.13 to 0.32, and 39.3 to 137.7 W/kg, respectively, depending on the operating conditions.

KEYWORDS:

• Chemisorption
• heat pump
• performance analysis
• operation strategy
• dynamic modeling

Nomenclature

A	=	Area [m2]
c	=	Specific heat [J/kg·K]
COP	=	Coefficient of performance [-]
h	=	Enthalpy [J/kg]
k	=	Thermal conductivity [W/m·K]
m	=	Mass [kg]
P	=	Pressure [Pa]
q	=	Heat transfer rate per unit volume [W/m3]
$\dot{q}$	=	Heat transfer rate per unit length [W/m]
r	=	Radius [m]
R	=	Gas constant [J/K·mol]
Rx	=	Reactor
SCP	=	Specific cooling power [-]
t	=	Time [s]
T	=	Temperature [K]
u	=	Velocity [m/s]
w	=	Mass flow rate [kg/s]
z	=	Length of axial direction [m]
Greek letters	=
ρ	=	Density [kg/m3]
φ	=	Conduction heat transfer rate per area [W/m2]
Subscripts	=
2nd	=	Secondary fluid
ADS	=	Adsorption
avg	=	Average
cond	=	Condenser
DES	=	Desorption
dr	=	Desorption reactor
EG	=	expanded graphite
eq	=	equilibrium
eva	=	Evaporator
fric	=	Friction loss
i	=	Inner
m	=	Material
nom	=	Nominal
o	=	Outer
rx1	=	Reactor 1
rx2	=	Reactor 2

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government (MOTIE) [20212050100010], Chemisorption heat pump system using electrochemical compressor).