ENERGETIC ANALYSIS OF AN ABSORPTION CHILLER USING NH<sub>3</sub>/LiNO<sub>3</sub> AS AN ALTERNATIVE WORKING FLUID

Lima, Alvaro A. S.; Ochoa, Alvaro A. V.; Costa, José Â. P. da; Santos, Carlos A. C. dos; Lima, Márcio V. F.; Menezes, Frederico D. de

doi:10.1590/0104-6632.20190362s20180473

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Thermodynamics • Braz. J. Chem. Eng. 36 (2) • Apr-Jun 2019 • https://doi.org/10.1590/0104-6632.20190362s20180473 copy

ENERGETIC ANALYSIS OF AN ABSORPTION CHILLER USING NH₃/LiNO₃ AS AN ALTERNATIVE WORKING FLUID

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This paper presents a thermodynamic model developed for a prototype absorption chiller using NH₃/LiNO₃ with 10 kW of nominal capacity. The study was undertaken using thermodynamic modeling based on the mass and energy balance, takes the overall heat transfer coefficients into consideration and uses the characteristic equation method. First, the results obtained from the thermodynamic modeling developed were compared with those obtained from the characteristic equations of thermal power activation and the cooling capacity. These showed good agreement with the experimental data, there being maximum relative errors of around 5% for most of the operational conditions of the system. Secondly, a parametric analysis was made by altering the variables, such as temperature, mass flow rate, and configuring the heat dissipation that influences the overall performance of the prototype chiller.

Keywords:
Prototype absorption chiller; Characteristic equation method; Parametric analysis; NH₃/LiNO₃

Mass Balance	Species Balance	Energy Balance
$\sum_{i n} \dot{m} = \sum_{o u t} \dot{m}$	$\sum_{i n} \dot{m} X_{x} = \sum_{o u t} \dot{m} X_{y}$	${\dot{E}}_{i n} = {\dot{E}}_{o u t}$
External Circuit – Heat Transfer Equations – of the Heat Exchangers
${\dot{Q}}_{x} = {\dot{m}}_{s o l} (h_{i n} - h_{o u t})$	${\dot{Q}}_{X} = U A_{X} ∆ T l m_{X}$	$Δ {Tlm}_{X} = \frac{(t_{X, in} - T_{X, in}) - (t_{X, out} - T_{X, out})}{Ln \{\frac{(t_{X, in} - T_{X, in})}{(t_{X, out} - T_{X, out})}\}}$

Generator	Absorber	Evaporator	Condenser
${\dot{Q}}_{G} = G ∙ {\dot{Q}}_{E} + {\dot{Q}}_{l o s s}$	${\dot{Q}}_{A} = A ∙ {\dot{Q}}_{E} + {\dot{Q}}_{l o s s}$	${\dot{Q}}_{E}$	${\dot{Q}}_{C} = C ∙ {\dot{Q}}_{E}$
Solution and Refrigerant Heat exchangers
${\dot{Q}}_{l o s s} = {\dot{Q}}_{m a x} - {\dot{Q}}_{s h e}$	${\dot{Q}}_{m a x} = {\dot{Q}}_{w e a k} (h_{4} - h_{1})$	$C = C^{'} ∙ R$
Generator - Absorber		Evaporator - Condenser
$G ∙ {\dot{Q}}_{E} + {\dot{Q}}_{l o s s} = U A_{G} (t_{G} - T_{G})$ $A ∙ {\dot{Q}}_{E} + {\dot{Q}}_{l o s s} = U A_{A} (T_{A} - t_{A})$		${\dot{Q}}_{E} = U A_{E} (t_{E} - T_{E})$ $C ∙ {\dot{Q}}_{E} = U A_{C} (T_{C} - t_{c})$
$A = \frac{(h_{10} - h_{4})}{(h_{10} - h_{8})}$	$G = \frac{(h_{7} - h_{4})}{(h_{10} - h_{8})}$	$R = \frac{(h_{10} - h_{20})}{(h_{20} - h_{19})}$	$C' = \frac{(h_{7} - h_{8})}{(h_{8} - h_{19})}$

Mass flows (kg.s^-1)		Temperatures (°C)
Hot water	0.8330	Inlet Hot water	90.0
Cold Water	0.8000	Inlet Cold water - Absorber	37.5
Chilled Water	0.7986	Inlet Cold water - Condenser	37.5
Rich Solution (NH₃/LiNO₃)	0.1000	Outlet Chilled Water	15.0
UA Product (kW K^-1)
Generator	3.69	Evaporator	1.56
Condenser	2.43	SHE	1.06
Absorber	3.00	RHE	0.05
Pump Efficiency (%)		100

Parameter [kW]	a (kW.K^-1)	b (kW.K^-1)	c (kW.K^-1)	d (kW)
${\dot{Q}}_{e_e x p_c o r r}$	0,50449	0,7957	0,32577	2,91347
${\dot{Q}}_{g_e x p_c o r r}$	0,55344	1,0164	0,48662	2,05125

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E-mail: rgiudici@usp.br

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[1] * Corresponding author: Alvaro A. O. Villa - E-mail: ochoaalvaro@recife.ifpe.edu.br

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ENERGETIC ANALYSIS OF AN ABSORPTION CHILLER USING NH3/LiNO3 AS AN ALTERNATIVE WORKING FLUID

Abstract

ENERGETIC ANALYSIS OF AN ABSORPTION CHILLER USING NH₃/LiNO₃ AS AN ALTERNATIVE WORKING FLUID